Dissertations / Theses: 'Iron-based superconductors'

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Friederichs, Gina. "Iron-based superconductors via soft chemistry." Diss., Ludwig-Maximilians-Universität München, 2015. http://nbn-resolving.de/urn:nbn:de:bvb:19-185306.

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Demirdis, Sultan. "Effects of disorder in iron-based superconductors." Palaiseau, Ecole polytechnique, 2012. https://pastel.hal.science/docs/00/77/89/43/PDF/thesis.pdf.

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L'ancrage des vortex est utilisé comme une sonde pour l'identification du type de désordre et son effet sur la supraconductivité dans la famille 122 des supraconducteurs à base de fer. Une nouvelle technique d'analyse obtenue d'images de décoration de Bitter prenant en compte l'interaction de chaque vortex avec ses voisins, a permis d'obtenir l'énergie et la force de piégeage dans Ba(Fe1-xCox)2As2, dans le régime de bas champ magnétique. La corrélation avec des mesures de courant critique Jc a montré que le piégeage des vortex dans ce composé est due à l'hétérogénéité des propriétés supraconductrices sur une échelle de 20-100 nm. Application de la même méthode d'analyse pour les vortex dans le BaFe2(As1-xPx)2 a montré que l'énergie et la force d'ancrage dépendent du dopage x. Les mesures de Jc et de la distribution des forces de piégeage ont montré que la distance moyenne entre différents centres de piégeage est de l'ordre de 90 nm et que cette distance augmente quand on augmente le conteneur en P. La combinaison de ces résultats avec les mesures de Jc mène à la conclusion que l'ancrage fort des lignes de flux due à l'hétérogénéité des propriétés supraconductrice à l'échelle de nm est à l'origine de la constante observé à des champ faibles dans les courbes de Jc ainsi que la diminution en loi de puissance qui suit. On traite également la contribution d'ancrage faible collectif à Jc, qui se manifeste à des champs magnétiques plus importants, de l'ordre de 1 T. Cette contribution a été analysée en terme de la diffusion des quasiparticules et de la fluctuation spatiale du libre parcours moyen. Afin de tester l'hypothèse avancé ci-dessus, l'irradiation aux électrons d'énergie 2. 5 MeV, sur les composés dopé au Co, Ni et P de la famille 122 a été réalisé à des différentes doses pour plusieurs dopage de ces matériaux. Ce type d'irradiation introduit des défauts ponctuels de taille atomique dans le matériau. La température critique Tc de tous les matériaux étudiés diminue après irradiation de façon similaire. Une claire augmentation de la contribution d'ancrage faible collectif à Jc dans le composé dopé au Co a été observée. De plus, cette contribution qui, avant irradiation, était absente dans tous les dopages du composé au P, apparait après irradiation. Les défauts ponctuels de taille atomique, diffuseur des quasiparticules, dans les supraconducteurs à base de fer sont donc à l'origine de la contribution d'ancrage faible collectif à Jc
The pinning of vortices is used as a probe for the identification of disorder and its effect on superconductivity in 122-type iron-based superconductors. Using a new analysis method taking into account the interaction of individual vortices with their neighbors, pinning energies and pinning forces in Ba(Fe1-xCox)2As2 are extracted from the vortex distributions in the regime of small fields. The correlation of measurements of the critical current density Jc with the spatial distribution of vortices shows that pinning in this particular regime is due to the heterogeneity of superconducting properties, on the scale of 20-100 nm. Application of the same analysis procedure on the vortex structure in BaFe2(As1-xPx)2 with less density fluctuations, shows that the pinning forces and energies depend on the doping level x. Both Jc measurements and pinning force distributions independently yield a mean distance between pinning centers of about 90 nm, increasing with increasing P-content x. Combination of the above results and critical current density measurements lead to the conclusion that the low field plateau observed in Jc curves, followed by a power-law decrease, emerges from strong pinning due to nm scale heterogeneity of superconducting properties. Attention is also paid to the weak collective pinning contribution that manifests itself at higher fields > 1 T. Notably, this contribution is consistently analyzed in terms of quasiparticle scattering and mean free path fluctuations. In order to test this premise irradiation of Co, Ni and P-doped 122-type iron-based compounds with high-energy 2. 5 MeV electrons is performed for several doping levels of the materials and to different doses. Such irradiation introduces atomic sized point-like defects. Following irradiation it appears that the critical temperature Tc shows a similar depression for all studied materials. The weak collective contribution to Jc in Co-doped is found to clearly increase. Moreover this contribution appears after irradiation of the P-doped compound in which it was previously absent. This allows one to confirm the role of atomic point-like pins as scatterers in Ni and Co-doped compounds, as well as the hypothesis that these defects are at the origin of the weak collective pinning contribution to Jc at larger fields

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Watson, Matthew D. "Electronic and magnetic properties of iron-based superconductors." Thesis, University of Oxford, 2015. https://ora.ox.ac.uk/objects/uuid:7239fcb6-8117-4023-b68e-c6bbe2d4af22.

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This thesis presents experimental studies of the electronic and magnetic properties of several iron-based unconventional superconductors, primarily using the techniques of magnetotransport and torque magnetometry in high magnetic fields and synchrotron-based angle-resolved photo-emission spectroscopy (ARPES). Superconductivity in the iron-based superconductors is always found in proximity to a magnetic phase, and the details of the electronic structure and Fermi surface are also important in determining the strength of interactions, and ultimately superconductivity. This motivates the experimental studies of electronic, magnetic and superconducting properties of Fe-based superconductors presented in this thesis. First, quantum oscillation measurements using high-field torque magnetometry are used to provide a partial determination of the Fermi surface of superconducting LiFeAs. The data are compared with density functional theory calculations, finding strong mass enhancements on the observed electron bands, however the hole bands are not observed. A large portion of this thesis concerns experiments on FeSe, which uniquely has a structural transition but is not magnetically ordered at any temperature. High field magnetotransport measurements show quantum oscillations, revealing small quasi-two dimensional Fermi surfaces, and it is argued that both hole and electron pockets are observed. The low-temperature Fermi surface consisting of one hole pocket and two electron pockets is also deduced from low-field magnetotransport. ARPES studies show that both hole and electron pockets undergo a significant elongation when cooling through the structural transition at ~90 K, interpreted as the result of orbital order. Measurements of the resistivity anisotropy above the structural transition are used to show that the structural distortion is electronically-driven. By combining these data sets, a complete picture of the symmetry-broken electronic structure of FeSe is constructed. The final chapter concerns another iron-based superconductor with a more complex crystal structure, the so-called ``10-3-8" phase, and in particular finds an unusual field-induced magnetic transition.

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Cassidy, Simon J. "Structure, properties, and chemistry of iron-based superconductors." Thesis, University of Oxford, 2015. https://ora.ox.ac.uk/objects/uuid:204b8645-b80f-4a71-8399-66f86edcfd9f.

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This thesis reports the synthesis and characterisation of several layered pnictides, chalcogenides, and oxychalcogenides, with an emphasis on materials that exhibit high temperature superconductivity. High and low temperature techniques have been used to synthesise new materials and modify their properties. The majority of this work has been focused on the synthesis of superconducting materials with the general formula Ax(NH3)y(NH2)zFeSe, where A is an alkali metal. These materials are formed from a co-intercalation of alkali metals, ammonia, and alkali metal amides into the interlamellar space of pre-formed tetragonal FeSe. There is a remarkable increase in Tc associated with this intercalation, from 8 K in FeSe to a maximum of 46 K in the products. A range of characterisation techniques including neutron and X-ray diffraction, EXAFS, and SQUID magnetometry have been used to identify a variety of crystal structures, compositions, and properties adopted by these materials. The synthesis procedure of these materials where, A = Na and K, has been studied in-situ via powder X-ray diffraction at world-class central facilities, revealing new phases, intermediates, and activation energies. The Kx(NH3)y(NH2)zFeSe phases are found to undergo a topotactic decomposition step to become Kx'Fe2-y'Se2 phases on annealing, which has also been studied by in-situ powder X-ray diffraction. Additional studies on Na1-xFe2-yAs2 and CaFeSeO have been performed. Na1-xFe2-yAs2 is the product of a room temperature deintercalation of sodium and iron from NaFeAs, which changes the superconducting properties of the material. XAFS measurements have been used to characterise the local structure of the materials, which supports the conclusion that iron is deintercalated from the parent material and gives new insight into the effect of the iron vacancies on the local structure. CaFeSeO is a newly discovered material that adopts a never-before-seen crystal structure, which has been solved from powder X-ray diffraction data. Intricate vacancy ordering exists in the material, which contributes to a peculiar mixture of magnetic behaviours including signatures of a spin glass, ordered antiferromagnet, and an ordered ferromagnetic component. All of these behaviours however, can be rationalised by the nuclear and magnetic structure of the material that have been refined using powder neutron diffraction.

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Wang, Qianen, and 王乾恩. "Electronic structures of impurity and orbital-resolved vortex core states in iron-selenide superconductors." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2014. http://hdl.handle.net/10722/206433.

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We study the effect of a single non-magnetic impurity and vortex core states in iron-selenide superconductors by solving the Bogoliubov-de Gennes equations self-consistently based on a three-orbital model. Various pairing symmetry are considered in the calculation. The impurity-induced in-gap bound states are found only for attractive impurity scattering potential, as in the cases of doping of Co or Ni, which is characterized by the strong particle-hole asymmetry, in the nodeless d_(x^2-y^2 ) wave pairing state. This property may be used to probe the pairing symmetry of iron-selenide 122-type superconductors. The orbital-resolved vortex core states of different pairing symmetries manifest themselves as distinguishable structures due to different behavior of the quasiparticle wavefunctions. The obtained vortices are classified by the invariant subgroups of the symmetry group of the meanfield Hamiltonian in the presence of magnetic field as isotropic s- and s±-wave vortices have G_5 symmetry for each orbital, whereas d_(x^2-y^2 ) wave vortices show G(* )¦6 symmetry for d_xzand d_yz orbitals and G(* )¦5 symmetry for d_xy orbital. In the case of d_(x^2-y^2 ) wave vortices, hybridized-pairing between d_xzand d_yz orbitals gives rise to a relative phase difference in terms of winding structures of vortices between these two orbitals and d_xy orbital, which is essentially caused by a transformation of co-representation of G(* )¦5 and G(* )¦6 subgroup. Calculation of particle densities show common charging feature of vortices in the cases of s± and d_(x^2-y^2 ) wave pairing states where the electron-like vortices are observed for d_xz and d_yz orbitals while hole-like vortices for d_xyorbital. The phase difference of orbital-resolved d_(x^2-y^2 ) wave vortices and their charging effects can be verified by further experimental observations.
published_or_final_version
Physics
Doctoral
Doctor of Philosophy

6

Serafin, Alessandro. "Penetration depth studies of cuprate and iron-based superconductors." Thesis, University of Bristol, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.549692.

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Using a high resolution susceptometer based on a self-resonant tunnel diode circuit, the temperature dependence of the London penetration depth λ(T) was measured in the cuprate superconductor YBa2Cu4O8 and in two iron-based superconductor materials (LaFePO,FeSe0.5 Te0.5). The first project investigated the role of CuO chains in the underdoped high- Tc cuprate YBa2CU4O8 in relation to the anisotropy observed in the in-plane components of the superfluid density [1][2]. The components of λ(T) relative to the three crystallographic axises were measured. An in-plane anisotropic response was revealed by a clear enhancement of the superfluid density along the chain direction (b-axis) at low temperature. A small DC magnetic field applied perpendicular to the CuO chain revealed a strong suppression of this extra screening current density. In terms of coupling between plane and chain bands, the result can be interpreted within a proximity-model with superconductivity induced in the intrinsically normal chains by the superconducting planes through the "proximity-effect' [3] [4] In the second project we studied the symmetry of the order parameter in iron- based superconductors. The linear T dependence of λ observed in LaFePO strongly suggested the presence of nodes in the gap function. The linearity evolved into a T2 dependence upon isovalent substitution of Y atoms on the La site supporting the conclusion of the existence of nodes where the gap changes sign. In contrast λ(T) in FeSe0.5Te0.5 followed a higher power-law T" with n=2.2±O.1. Such behaviour can be taken as evidence for strong pair breaking within a sign-changing pairing state either with or, more likely according to other experimental results (thermal conductivity in particular), without nodes. Heat-capacity measurements were also performed on this material revealing a field dependence close to the transition which resembles the high- Tc cuprates behaviour with evidences of strong thermal fluctuations. Interestingly such fluctuations appear to have unusual anisotropic effects in FeSe0.5Te0.5.

7

Dioguardi, Adam Paul. "Nuclear Magnetic Resonance Studies of the 122 Iron-Based Superconductors." Thesis, University of California, Davis, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3602046.

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Extensive ⁷⁵As nuclear magnetic resonance (NMR) studies were conducted on a variety of 122 iron-based superconductors. NMR frequency swept spectra and the spin-lattice relaxation rate (T₁^-1) were measured in CaFe₂As₂ as a function of temperature. The temperature dependence of the internal hyperfine field was extracted from the spectra, and T₁^-1 exhibits an anomalous peak attributed to the glassy freezing of domain walls associated with filamentary superconductivity. The field dependence of T₁^-1 and subsequent bulk resistivity and magnetization measurements also show signatures of filamentary superconductivity nucleated at antiphase domain walls. Systematic doping-dependent NMR studies were also carried out on Ni- and Co-doped BaFe₂As₂. In the Ni-doped variant, local magnetic inhomogeneities were observed via field swept NMR spectral analyses, and the doping dependence of the Néel temperature T_N was confirmed by fits to (T₁T)^-1(T). Spectral wipeout and stretched exponential relaxation behavior in the Co-doped variant reveal inhomogeneous behavior and the emergence of a cluster spin glass state. The NMR measurements bring into question the details of the phase transition from coexisting antiferromagnetism and superconductivity to pure superconductivity.

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Neupane, Madhab. "Angle-Resolved Photoemission Studies on Ruthenates and Iron-Based Superconductors." Thesis, Boston College, 2010. http://hdl.handle.net/2345/1944.

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Thesis advisor: Ziqiang Wang
Angle-resloved photoemission spectroscopy (ARPES) is a powerful technique to study the electronic structure in solids. Its unique ability of resolving the energy and momentum information of electrons inside a solid provides an essential tool in measuring the electronic structure of solids. ARPES has made great contributions in the understanding of correlated system such as high-T_c superconductors and ruthenates. The Metal-insulator transition is a fundamental problem in condensed matter physics. The calcium substituted strontium ruthenate, Ca_2-xSr_xRuO₄, provides a good platform to study the metal-insulator transition in multi-orbital systems. This system has a complex phase diagram that evolves from a p-wave superconductor to a Mott insulator. One of important projects of this thesis focuses on Ca_2-xSr_xRuO₄ The growing evidence for coexistence of itinerant electrons and local moments in transition metals with nearly degenerate d orbitals suggests that one or more electron orbitals undergo a Mott transition while the others remain itinerant. We have observed a novel orbital selective Mott transition (OSMT) in Ca_1.8Sr_0.2RuO₄ by ARPES. While we observed two sets of dispersing bands and Fermi surfaces (FSs) associated with the doubly-degenerate d_yz and d_zx orbitals, the Fermi surface associated with the d_xy orbital which has a wider bandwidth is missing as a consequence of selective Mott localization. Our theoretical calculations have demonstrated that this unusual OSMT is mainly driven by the combined effects of inter-orbital carrier transfer, superlattice potentials and orbital degeneracy, whereas the bandwidth difference plays a less important role. Another important project of this thesis focuses on the recently discovered iron-pnictides superconductors. The idea of inter-FS scattering associated with the near-nesting condition has been proposed to explain the superconductivity in the pnictides. The near-nesting condition varies upon the carrier doping which shifts the chemical potential. We have performed a systematic photoemission study of the chemical potential shift as a function of doping in a pnictide system based on BaFe₂As₂. The experimentally determined chemical potential shift is consistent with the prediction of a rigid band shift picture by the renormalized first-principle band calculations. This leads to an electron-hole asymmetry (EHA) due to different Fermi velocities for different FS sheets, which can be calculated from the Lindhard function of susceptibility. This built-in EHA from the band structure, which is fully consistent with the experimental phase diagram, strongly supports that inter-FS scattering over the near-nesting Fermi surfaces plays a vital role in the superconductivity of the iron pnictides
Thesis (PhD) — Boston College, 2010
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Physics

9

Taylor, Alice Elizabeth. "Magnetic dynamics in iron-based superconductors probed by neutron spectroscopy." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:d6be2dd2-9d8a-48fd-a290-c31dd436a972.

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This thesis describes inelastic neutron scattering (INS) experiments on several iron-based materials. The experiments were primarily designed to investigate the link between magnetic dynamics and superconductivity. The work contributes to evidence that magnetic fluctuations influence or are influenced by superconductivity. It is demonstrated that the INS response of a material, in conjunction with theoretical models, can provide valuable information about both superconductivity and magnetism. I measured the magnetically ordered parent-compound SrFe2As2 to investigate the nature of magnetism in iron-based systems. Comparison of the data to models based on both itinerant and localised magnetism showed that an itinerant model offers the best description of the data. LiFeAs is a superconductor that shows no magnetic order, however I was able to distinguish a magnetic signal in its INS spectrum. The signal is consistent with the magnetic resonance observed in several other iron-based superconductors. This indicates that LiFeAs likely hosts an s± gap symmetry. I investigated two iron-phosphide systems, LaFePO and Sr2ScO3FeP, and in this case I was unable to identify any magnetic scattering. Comparison to LiFeAs showed that any signal in LaFePO is at least 7 times weaker. These results suggest that magnetic fluctuations are not as influential to the electronic properties of iron-phosphide systems as they are in other iron-based superconductors. In CsxFe2−ySe2 I found two independent signals that appear to be related to phase-separated magnetic and superconducting regions of the sample. I showed that fluctuations associated with the magnetically ordered phase are consistent with localised magnetism, and do not respond to superconductivity. The second signal, however, increases in intensity below the superconducting transition temperature Tc = 27K, consistent with a magnetic resonance. This could be indicative of a pairing symmetry in CsxFe2−ySe2 that is distinct from most other iron-based superconductors. Finally, the molecular intercalated FeSe compound Li0.6(ND2)0.2(ND3)0.8Fe2Se2 revealed strong magnetic fluctuations. Again the signal was consistent with a magnetic resonance responding to Tc = 43 K. The results suggest that Lix(ND2)y(ND3)1−yFe2Se2 is similar to the superconducting phase of CsxFe2−ySe2, placing constraints on theoretical models to describe the molecular intercalated FeSe compounds.

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Friederichs, Gina [Verfasser], and Dirk [Akademischer Betreuer] Johrendt. "Iron-based superconductors via soft chemistry / Gina Friederichs. Betreuer: Dirk Johrendt." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2015. http://d-nb.info/1075456770/34.

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Shermadini, Zurab. "Iron based pnictide and chalcogenide superconductors studied by muon spin spectroscopy." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-148934.

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In the present thesis the superconducting properties of the Iron-based Ba_{1-x}Rb_{x}Fe_{2}As_{2} arsenides, and A_{x}Fe_{2-y}Se_{2} (A = Cs, Rb, K) chalcogenides are investigated by means of Muon Spin Rotation Spectroscopy. The temperature and pressure dependence of the magnetic penetration depth is obtained form muSR experiments and analyzed to probe the superconducting gap-symmetries for each samples. The Ba_{1-x}Rb_{x}Fe_{2}As_{2} system is described within the multi-gap s+s-wave scenario and results are discussed in the light of the suppression of inter-band processes upon hole doping. Due to the lowered upper critical field Bc2 and reduced Tc, a large section of B-T-p phase diagram is studied for the hole-overdoped x=1 case. By applying hydrostatic pressure, the RbFe_{2}As_{2} system exhibits a classical BCS superconducting characteristics. The A_{x}Fe_{2-y}Se_{2} chalcogenide represents a system containing magnetically ordered and superconducting phases simultaneously. In all investigated chalcogenide samples, about 90% of the total volume show the strong antiferromagnetic phase and 10% exhibit a paramagnetic behavior. Magnetization measurements reveal a 100% Meissner effect, while muSR clearly indicates that the paramagnetic phase is a perfect superconductor. Up to now, there is no clear evidence whether the antiferromagnetic phase is also superconducting. The microscopic coexistence and/or phase separation of superconductivity and magnetism is discussed. Moreover, a new hydrostatic double-wall pressure cell is developed and produced, satisfying the demands of muSR experiments. The designs and characteristics of the new pressure cell are reviewed in the present thesis.

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Niestemski, Francis Charles. "Bosonics in the Copper and Iron based High Transition Temperature Superconductors." Thesis, Boston College, 2009. http://hdl.handle.net/2345/1409.

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Thesis advisor: Vidya Madhavan
It has been long established that the phenomenon of superconductivity is administered by lattice deformations (phonons) which act to pair electrons into spinless bosons free to condense into a coherent ground state. This superconducting phase is protected up to a critical temperature above which thermal fluctuations are potent enough to destroy the resistance free phase. The strength of this phonon mediation has been calculated by strong coupling theory and found to be capable of accommodating pairing up to near 40 K. So with the advent of copper-oxide (cuprate) superconductors boasting transitions temperatures exceeding 90 K it was clear that these material represented a new breed of superconducting physics. More than twenty years after the initial discovery of these high-transition temperatures the most basic questions are yet to be answered, the most fundamental of which is by what mechanism does pairing occur? The field splits between those who feel that a boson mediator is still necessary to act as the virtual glue which binds electrons into cooper pairs while others insist that really the Coulomb force alone is enough to induce pairing physics. Even within the boson-seeker community there is no consensus on what particular type of boson is contained in this system whether it be a lattice excitation or spin excitation. This answer has been clouded by previous experimental results on the hole-doped cuprates which have made strong cases for every scenario rendering them largely inconclusive. For this answer though it is possible to explore materials that have not yet been clouded by conflicting results by performing the first high resolution ultra-high-vacuum low-temperature scanning tunneling microscopy (STM) study of an electron-doped cuprate. A distinct and unambiguous bosonic mode is found at energy near 10.5 meV. Through comparison with other experimental data it is found that this mode does not fit the characteristics of a phonon. It is found, through comparison with neutron scattering experiments on the same sample, that this mode is consistent with a spin collective mode. Further more it is found that this mode is linked with the strength of superconductivity nominating it as the possible electron pairing mechanism. Doping and temperature dependence studies are performed to investigate this possibility. Finally the same procedures developed can be applied to the newly discovered iron based superconductors which may represent yet another type of new superconductor physics. Initial results on the first bosonic mode STM study of SrFe$_{2-x}$Co$_{x}$As$_{2}$ and BaFe$_{2-x}$Co$_{x}$As$_{2}$ are presented
Thesis (PhD) — Boston College, 2009
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Physics

13

Malone, Liam Douglas. "The gap symmetry of the organic and iron based pnictide superconductors." Thesis, University of Bristol, 2009. http://hdl.handle.net/1983/ec8fb6fa-505b-42c4-b8ea-c128575336b3.

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Schmiedt, Jacob. "Interplay of magnetic, orthorhombic, and superconducting phase transitions in iron-based superconductors." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-154434.

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The physics of iron pnictides has been the subject of intense research for half a decade since the discovery of superconductivity in doped LaFeAsO in 2008. By now there exists a large number of different materials that are summarized under the term "pnictides'' with significant differences in their crystal structure, electronic properties, and their phase diagrams. This thesis is concerned with the investigation of the various phase transitions that are observed in the underdoped compounds of the pnictide subgroups RFeAsO, where R is a rare-earth element, and AFe_2As_2, where A is an alkaline-earth element. These compounds display two closely bound transitions from a tetragonal to an orthorhombic phase and from a paramagnetic to an antiferromagnetic metal. Both symmetry-broken phases are suppressed by doping or pressure and close to their disappearance superconductivity sets in. The superconducting state is stabilized until some optimal doping or pressure is reached and gets suppressed thereafter. The central goal of this thesis is to improve our understanding of the interplay between these three phases and to describe the various phase transitions. We start from an itinerant picture that explains the magnetism as a result of an excitonic instability and show how the other phases can be included into this picture. This approach is based on the the observation that the compounds we are interested in have a Fermi surface with multiple nested electron and hole pockets and that they have small to intermediate interaction strengths. The thesis starts with a study of the doping dependence of the antiferromagnetic phase transition in four different five-orbital models. We use the random-phase approximation to determine the transition temperature, the dominant ordering vector, and the contribution of the different orbitals to the ordering. This allows us to identify the more realistic models, which give results that are in good agreement with experimental observations. In addition to the frequently made assumption of orbital-independent interaction potentials we study the effect of a reduction of the interaction strengths that involve the d_{xy} orbital. We find that this tunes the system between two different nesting instabilities. A reduction of the interactions that involve the d_{xy} orbital also enhances the tendency towards incommensurate (IC) order. For a weak reduction this tendency is compensated by the presence of the orthorhombic phase. However, for a reduction of 30%, as it is suggested by constrained random-phase-approximation calculations, we always find large doping ranges, where a state with IC order has the highest transition temperature. We continue the investigation of the magnetic phase transition by studying the competition of different possible types of antiferromagnetic order that arises from the presence of two degenerate nesting instabilities with the ordering vectors (pi,0) and (0,pi). We derive a Ginzburg-Landau free energy from a microscopic two-band model and find that the presence of the experimentally observed stripe phase strongly depends on the number and size of the hole pockets in the system and on the doping. We show that within the picture of a purely magnetically driven nematic phase transition, which breaks the C_4 symmetry and induces the orthorhombic distortion, the nematic phase displays exactly the same dependence on the model parameters as the magnetic stripe phase. We propose that in addition to the purely magnetically driven nematic instability there is a ferro-orbital instability in the system that stabilizes the nematic transition and, thus, explains the experimentally observed robustness of the orthorhombic transition. We argue that including a ferro-orbital instability into the picture may also be necessary to reproduce the transition from simultaneous first-order transitions into an orthorhombic antiferromagnetic state to two separate second-order transitions, which is observed as a function of doping. Finally, a study of the superconducting phase transition inside the antiferromagnetic phase that is observed in some pnictide compounds is presented. We present an approach to calculate the fluctuation-mediated pairing interaction in the spin-density-wave phase of a multiband system, which is based on the random-phase approximation. This approach is applied to a minimal two-band model for the pnictides to study the effect of the various symmetry-allowed bare on-site interactions on the gap symmetry and structure. We find a competition between various even- and odd-parity states and over a limited parameter range a p_x-wave state is the dominant instability. The largest part of the parameter space is dominated by even parity states but the gap structure sensitively depends on the bare interactions. We propose that the experimentally observed transition from a nodeless to a nodal gap can be due to changes in the on-site interaction potentials.

15

Price, Stephen [Verfasser]. "Interplay between magnetism and superconductivity in iron based high temperature superconductors / Stephen Price." Aachen : Hochschulbibliothek der Rheinisch-Westfälischen Technischen Hochschule Aachen, 2013. http://d-nb.info/1051419441/34.

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Hammerath, Franziska. "Magnetism and Superconductivity in Iron-based Superconductors as Probed by Nuclear Magnetic Resonance." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-89865.

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Nuclear Magnetic Resonance (NMR) has been a fundamental player in the studies of superconducting materials for many decades. This local probe technique allows for the study of the static electronic properties as well as the low energy excitations of the electrons in the normal and the superconducting state. On that account it has also been widely applied to Fe-based superconductors from the very beginning of their discovery in February 2008. This dissertation comprises some of these very first NMR results, reflecting the unconventional nature of superconductivity and its strong link to magnetism in the investigated compounds LaO(1-x)F(x)FeAs and LiFeAs.

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Mohamed, Mahmoud. "Physical Properties of Iron-based Superconductors Probed by Low-Temperature Specific-Heat Measurements." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-98736.

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In this thesis, specific heat, magnetic susceptibility and resistivity studies on the iron-pnictide superconductors LiFeAs, NaFe1-xCoxAs, AFe2As2 (A = K, Ca, Ba), M1-xNaxFe2As2 (M = Ca, Ba), and Ca(Fe1-xCox)2Fe2As2 are presented, from which different intrinsic physical properties are resolved. The combined first-order spindensity wave/structural transition which occurs in the parent compounds of the 122 pnictide systems is shown to gradually shift to lower temperature for low doping levels. Upon higher doping, this transition is completely suppressed and simultaneously, superconductivity appears at lower temperature. In contrast, the phase diagram in Ca(Fe1-xCox)2Fe2As2 is shown to exhibit a pronounced region of coexistence of magnetism and superconductivity. Further important results reported in this work concern the electronic properties and superconducting-gap characteristics. In LiFeAs, the zero-field temperature dependence of the electronic specific heat can be well described by two s-wave gaps, whose magnitudes are in agreement with ARPES results. Our gap analysis in KFe2As2, Ca0.32Na0.68Fe2As2, and Ba0.65Na0.35Fe2As2 single crystals also implies the presence of two s-wave-like gaps. The magnetic phase diagram of LiFeAs and KFe2As2 for magnetic fields along both principal orientations has been constructed and an anisotropy of Hc2(T) of 3 and 5, respectively, has been obtained.

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Park, Jitae Verfasser], and Bernhard [Akademischer Betreuer] [Keimer. "Spin dynamics in 122-type iron-based superconductors / Jitae Park. Betreuer: Bernhard Keimer." Stuttgart : Universitätsbibliothek der Universität Stuttgart, 2012. http://d-nb.info/1025256255/34.

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Jandke, Jasmin Maria [Verfasser]. "Elastic and Inelastic Scanning Tunneling Spectroscopy on Iron-Based Superconductors / Jasmin Maria Jandke." Karlsruhe : KIT Scientific Publishing, 2019. http://d-nb.info/1184402590/34.

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Jandke, Jasmin [Verfasser]. "Elastic and Inelastic Scanning Tunneling Spectroscopy on Iron-Based Superconductors / Jasmin Maria Jandke." Karlsruhe : KIT Scientific Publishing, 2019. http://d-nb.info/1184402590/34.

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Huang, Xinyi. "Novel Physical Phenomena of Iron-Based Superconductors Revealed Through Transport and Thermodynamic Measurements." Kent State University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=kent1491943156716437.

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22

Waßer, Florian Tim [Verfasser], Markus [Gutachter] Braden, and Thomas [Gutachter] Lorenz. "Magnetic Excitations in Iron-based Superconductors / Florian Tim Waßer ; Gutachter: Markus Braden, Thomas Lorenz." Köln : Universitäts- und Stadtbibliothek Köln, 2018. http://d-nb.info/1175091618/34.

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23

Mizukami, Yuta. "Effect of impurity scattering and electron correlations on quasiparticle excitations in iron-based superconductors." 京都大学 (Kyoto University), 2016. http://hdl.handle.net/2433/215210.

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Aluru, Rama K. P. "Spectroscopic imaging STM study of the interplay between magnetism and superconductivity in iron-based superconductors." Thesis, University of St Andrews, 2017. http://hdl.handle.net/10023/12048.

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Abstract:

The discovery of high-temperature superconductivity in 1986 in copper-oxide materials have opened up new avenues to investigate new families of quantum materials that were previously not known. Understanding the mechanism of superconductivity in high-T[sub]c superconductors has been an important research theme in condensed matter physics, as it is believed to be essential to realize the next generation engineered materials that become superconducting at room temperature. Discovered in 2006, iron based superconductors are a new addition to the family of high-T[sub]c superconductors, these materials exhibit several interesting properties and show some vivid similarities with cuprates and other families of high-temperature superconductors. In this thesis, I will present the spin-polarized scanning tunneling microscopy (SPSTM) study carried out on the parent compound of iron chalcogenide high temperature superconductor Fe[sub](1+y)Te to investigate the bi-collinear antiferromagnetic order. Magnetic tips in this work are prepared using a novel preparation technique by picking up excess iron atoms and clusters of FeTe from the surface of the sample. Next, I will present the SP-STM results obtained in the spin glass phase of Fe[sub](1+y)SeₓTe₁₋ₓ visualizing the interplay between the short ranged bi-directional bi-collinear antiferromagnetic order and superconductivity at the atomic scale. In this thesis, I will also present the scanning tunneling microscopy and spectroscopy (STM/STS) study of the native and engineered defect bound states in the iron-pnictide superconductor LiFeAs. This study addresses the pairing symmetry of the superconducting order parameter and understanding of dip-hump features seen in STM spectra outside the superconducting gap in iron pnictide superconductor LiFeAs.

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Frankovsky, Rainer. "Iron based superconductors and related compounds synthesized by solid state metathesis and high temperature reactions." Diss., Ludwig-Maximilians-Universität München, 2013. http://nbn-resolving.de/urn:nbn:de:bvb:19-157843.

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Rodríguez, Mota Rosa. "Using a flux threaded composite loop to identify the pairing symmetry of iron based superconductors." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=119730.

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Abstract:

Identifying the correct order parameter structure of the iron based superconductors family will provide insight about the pairing mechanism in these materials. Due to their multi-orbital band structure, the proximity of the superconducting phase to an anti-ferromagnetic phase, and the fact that superconductivity on these materials is associated to the Fe-pnictide layer, most theories favour an unconventional pairing mechanism, and an s± pairing symmetry, which changes signs between the electron and hole Fermi pockets. However, as most experiments are only sensitive to the magnitude of the order parameter and theoretical proposals for phase sensitive experiments are challenging, the s± structure remains unconfirmed. In 2010, Chen et al. performed a phase sensitive experiment that showed evidence of integer flux quantum and half integer flux quantum jumps in a Nb- NdFeAsO_0.88F_0.12 composite loop (Chen et al., 2010). This experiment has been interpreted as evidence of the predicted s± pairing symmetry. Inspired by these results, we present a microscopic lattice model to study the energy dependence on flux for an iron-pnictide/s-wave superconductor composite loop.
Identifier la structure du paramètre d'ordre de la famille de supraconducteurs à base de fer permettrait de mieux comprendre le mécanisme de création de paires dans ces matériaux. En raison de leur structure de bande multi-orbitale, de la proximité entre leur phase supraconductrice et anti-ferromagnétique ainsi que de la relation entre la supraconductivité et la couche Fe-pnictide qui leur être propre, la plupart des théories favorisent pour ces matériaux un mécanisme de formation de paires non-conventionnel. Les modèles théoriques prévoient également une symétrie s± dans la formation des paires, qui change de signe entre les électrons et les trous dans la surface de Fermi. Néanmoins, puisque les expériences actuelles ne sont sensibles qu'à la grandeur du paramètre d'ordre, la structure s± reste à confirmer. En 2010, Chen et al. ont exécuté une expérience sensible à la phase ayant montré l'existence de transitions de multiples entiers et demi-entiers de quantum de flux entier dans une boucle composite de Nb- NdFeAsO_0.88F_0.12 (Chen et al., 2010). Cette expérience a été interprétée comme une évidence de la symétrie s± dans la formation de paires. Inspirées par ces résultats, nous présentons un modèle de réseau microscopique pour étudier la dépendance en flux de l'énergie dans une boucle composite supraconductrice de fer-pnictide et un supraconducteur s sphérique.

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Friemel, Gerd [Verfasser], and Bernhard [Akademischer Betreuer] Keimer. "Itinerant spin dynamics in iron-based superconductors and cerium-based heavy-fermion antiferromagnets / Gerd Friemel. Betreuer: Bernhard Keimer." Stuttgart : Universitätsbibliothek der Universität Stuttgart, 2014. http://d-nb.info/1054330247/34.

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Diaconu, Andrei. "Ultra-low Temperature Measurements of London Penetration Depth in Iron Selenide Telluride Superconductors." ScholarWorks@UNO, 2013. http://scholarworks.uno.edu/td/1731.

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Abstract:

The newly discovered iron based superconductors have captivated the attention of the scientific community due to the unusual mechanism behind their superconductivity and their promise as the next generation high temperature superconductors. After a century of superconductor research, the physical mechanism behind high temperature superconductivity is still not understood. These new materials bring renewed hope in elucidating the pairing mechanism responsible with high temperature superconductors and achieving the ultimate goal of the field, room temperature superconductivity. Consequently, a deeper understanding of the intriguing properties of iron based materials is essential. A great deal about the pairing mechanism of Cooper electron pairs can be inferred from the symmetry of their pairing wave function or order parameter. One of the most involved probes for studying the pairing symmetry is the London penetration depth. The low temperature behavior of London penetration depth in superconductors is directly related to the density of states and provides a powerful tool for investigating low-lying quasiparticle energy and, for this very reason, can give valuable hints on superconducting gap symmetry. The work presented focuses on investigating the pairing symmetry in the Fe1+y(Te1−xSex) system using a radio-frequency tunnel diode oscillator (TDO) technique for precise measurements of the temperature dependence of their in-plane penetration depth. The TDO technique, based on an original concept involving the use of planar inductors in an novel configuration, was implemented on a dilution refrigerator to investigate a significant number of single crystal samples, with nominal Se concentrations of 36%, 40%, 43% and 45% respectively, down to temperatures as low as 50 mK. A systematic study together with a comprehensive analysis regarding the order parameter symmetry in the Fe1+y(Te1−xSex) system is presented. In many cases we found that London penetration depth shows an upturn below at low temperatures, indicative of a paramagnetic-type contribution. Also the low-temperature behavior of penetration depth is best described by a quadratic power law with no systematic dependence on the Se concentration. Most importantly, in the limit of T → 0, in some samples we observed a narrow region of linear temperature dependence, suggestive of nodes in the superconducting gap of Fe1+y(Te1−xSex).

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Jandke, Jasmin Maria [Verfasser], and W. [Akademischer Betreuer] Wulfhekel. "Elastic and Inelastic Scanning Tunneling Spectroscopy on Iron-Based Superconductors / Jasmin Maria Jandke ; Betreuer: W. Wulfhekel." Karlsruhe : KIT-Bibliothek, 2017. http://d-nb.info/1148551247/34.

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Jandke, Jasmin [Verfasser], and W. [Akademischer Betreuer] Wulfhekel. "Elastic and Inelastic Scanning Tunneling Spectroscopy on Iron-Based Superconductors / Jasmin Maria Jandke ; Betreuer: W. Wulfhekel." Karlsruhe : KIT-Bibliothek, 2017. http://d-nb.info/1148551247/34.

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31

Classen, Laura [Verfasser], and Michael [Akademischer Betreuer] Scherer. "Competing Orders in Strongly Correlated Systems - Dirac Materials and Iron-Based Superconductors / Laura Classen ; Betreuer: Michael Scherer." Heidelberg : Universitätsbibliothek Heidelberg, 2016. http://d-nb.info/1180736907/34.

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Um, Youngje [Verfasser], and Bernhard [Akademischer Betreuer] Keimer. "A study of lattice dynamics in iron-based superconductors by inelastic light scattering / Youngje Um. Betreuer: Bernhard Keimer." Stuttgart : Universitätsbibliothek der Universität Stuttgart, 2014. http://d-nb.info/1049688813/34.

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Herbig, Alexander [Verfasser], and H. von [Akademischer Betreuer] Löhneysen. "Ab-initio Electronic Structure Method for Substitutional Disorder Applied to Iron-Based Superconductors / Alexander Herbig. Betreuer: H. von Löhneysen." Karlsruhe : KIT-Bibliothek, 2016. http://d-nb.info/1103573942/34.

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34

Hazra, Tamaghna. "Theoretical studies of topology and strong correlations in superconductors." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1595547450594436.

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Frankovsky, Rainer [Verfasser], and Dirk [Akademischer Betreuer] Johrendt. "Iron based superconductors and related compounds synthesized by solid state metathesis and high temperature reactions / Rainer Frankovsky. Betreuer: Dirk Johrendt." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2013. http://d-nb.info/1036101169/34.

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Kretzschmar, Florian [Verfasser], Rudolf [Akademischer Betreuer] Gross, and Christian [Akademischer Betreuer] Pfleiderer. "Nematic Fluctuations, Fermiology and the Pairing Potential in Iron-Based Superconductors / Florian Kretzschmar. Gutachter: Rudolf Gross ; Christian Pfleiderer. Betreuer: Rudolf Gross." München : Universitätsbibliothek der TU München, 2015. http://d-nb.info/1076359728/34.

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Guterding, Daniel [Verfasser], Roser [Akademischer Betreuer] [Gutachter] Valenti, Igor I. [Gutachter] Mazin, and Rafael [Gutachter] Fernandes. "Microscopic modelling of organic and iron-based superconductors / Daniel Guterding ; Gutachter: Roser Valenti, Igor I. Mazin, Rafael Fernandes ; Betreuer: Roser Valenti." Frankfurt am Main : Universitätsbibliothek Johann Christian Senckenberg, 2017. http://d-nb.info/1134952279/34.

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Kretzschmar, Florian Verfasser], Rudolf [Akademischer Betreuer] [Gross, and Christian [Akademischer Betreuer] Pfleiderer. "Nematic Fluctuations, Fermiology and the Pairing Potential in Iron-Based Superconductors / Florian Kretzschmar. Gutachter: Rudolf Gross ; Christian Pfleiderer. Betreuer: Rudolf Gross." München : Universitätsbibliothek der TU München, 2015. http://nbn-resolving.de/urn:nbn:de:bvb:91-diss-20150820-1273389-1-0.

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Schmiedt, Jacob [Verfasser], Carsten [Akademischer Betreuer] Timm, and Peter [Akademischer Betreuer] Hirschfeld. "Interplay of magnetic, orthorhombic, and superconducting phase transitions in iron-based superconductors / Jacob Schmiedt. Gutachter: Carsten Timm ; Peter Hirschfeld. Betreuer: Carsten Timm." Dresden : Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://d-nb.info/106844889X/34.

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Böhmer, Anna Elisabeth [Verfasser], and H. von [Akademischer Betreuer] Löhneysen. "Competing Phases in Iron-Based Superconductors Studied by High-Resolution Thermal-Expansion and Shear-Modulus Measurements / Anna Elisabeth Böhmer. Betreuer: H. v. Löhneysen." Karlsruhe : KIT-Bibliothek, 2014. http://d-nb.info/1056955880/34.

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41

Shermadini, Zurab [Verfasser], Hans-Henning [Akademischer Betreuer] Klauß, and Clemens [Akademischer Betreuer] Laubschat. "Iron based pnictide and chalcogenide superconductors studied by muon spin spectroscopy / Zurab Shermadini. Gutachter: Hans-Henning Klauß ; Clemens Laubschat. Betreuer: Hans-Henning Klauß." Dresden : Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://d-nb.info/1068447737/34.

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42

Kaneko, Ulisses Ferreira 1984. "Phase transitions and electronic fluctuations in iron-based pnictides = Transições de fase e flutuações eletrônicas em pnictídeos à base de ferro." [s.n.], 2017. http://repositorio.unicamp.br/jspui/handle/REPOSIP/322478.

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Abstract:

Orientador: Eduardo Granado Monteiro da Silva
Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin
Made available in DSpace on 2018-09-01T17:31:34Z (GMT). No. of bitstreams: 1 Kaneko_UlissesFerreira_D.pdf: 51229533 bytes, checksum: 3d39a6722771458fa1812d75c31661b4 (MD5) Previous issue date: 2017
Resumo: Nesta tese, empregamos espectroscopia Raman para realizar um estudo detalhado dos fônons e das respostas eletrônicas em monocristais de LaFeAsO. Nós observamos as simetrias e frequências dos fônons nas fases tetragonal e ortorrômbica e também a dependência com a temperatura de um pico quase-elástico (do inglês: QEP) na simetria B1g com intensidade máxima em torno da transição magnética TN . A área e a altura do QEP B1g foram atribuídas às flutuações nemáticas de spin, enquanto que a largura do QEP B1g foi relacionada com taxa de relaxação dessas flutuações. Através da análise da largura do QEP B1g propomos que a transição estrutural esté relacionada a um congelamento gradual das flutuaçõees nemáticas de spin, o que deve ser um fenômeno geral presente nos demais supercondutores à base de Fe. Esse estudo foi complementado por medidas de espectroscopia Raman em BaFe2As2 e de difração de raios-X com luz síncrotron em LaFeAsO, BaFe2As2 e SrFe2As2 dopado com Co. Paralelamente, nós estudamos as estruturas cristalinas e magnéticas em compostos da série Ba1?xLaxTi1/2Mn1/2O3 através da técnica de difração de nêutrons
Abstract: In this thesis, we employed Raman spectroscopy to perform a detailed study of the phonons and electronic responses in single crystals of the LaFeAsO. We observed the symmetries and frequencies of the phonons in the tetragonal and orthorhombic phases and also the temperature dependence of the quasi-elastic peak (QEP) in the B 1g symmetry with maximum intensity around the magnetic transition T N . The B 1g QEP area and height were ascribed to spin nematic fluctuations, while the B 1g QEP width was related to the relaxation rate of these fluctuations. From the B 1g QEP width analysis we propose that the structural transition is related to a gradual freezing of the spin nematic fluctuations, which may be a general phenomenon present in other Fe-based superconductors. This study was complemented by measurements of Raman spectroscopy in BaFe2As2 and synchrotron X-ray diffraction in LaFeAsO, BaFe2As2 and Co-doped SrFe2As2 . In parallel, we studied the crystal and magnetic structures in compounds of the series Ba1?xLaxTi1/2Mn1/2O3 through the neutron diffraction technique
Doutorado
Física
Doutor em Ciências
140978/2012-7
CNPQ

43

Marra, Pasquale. "Theoretical approach to Direct Resonant Inelastic X-Ray Scattering on Magnets and Superconductors." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-185619.

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The capability to probe the dispersion of elementary spin, charge, orbital, and lattice excitations has positioned resonant inelastic x-ray scattering (RIXS) at the forefront of photon science. In this work, we will investigate how RIXS can contribute to a deeper understanding of the orbital properties and of the pairing mechanism in unconventional high-temperature superconductors. In particular, we will show how direct RIXS spectra of magnetic excitations can reveal long-range orbital correlations in transition metal compounds, by discriminating different kind of orbital order in magnetic and antiferromagnetic systems. Moreover, we will show how RIXS spectra of quasiparticle excitations in superconductors can measure the superconducting gap magnitude, and reveal the presence of nodal points and phase differences of the superconducting order parameter on the Fermi surface. This can reveal the properties of the underlying pairing mechanism in unconventional superconductors, in particular cuprates and iron pnictides, discriminating between different superconducting order parameter symmetries, such as s, d (singlet pairing) and p wave (triplet pairing).

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Hammerath, Franziska [Verfasser], Bernd [Akademischer Betreuer] Büchner, and Nicholas J. [Akademischer Betreuer] Curro. "Magnetism and Superconductivity in Iron-based Superconductors as Probed by Nuclear Magnetic Resonance / Franziska Hammerath. Gutachter: Bernd Büchner ; Nicholas J. Curro. Betreuer: Bernd Büchner." Dresden : Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2012. http://d-nb.info/1068148039/34.

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Mohamed, Mahmoud [Verfasser], Anja [Akademischer Betreuer] Wolter-Giraud, Bernd [Akademischer Betreuer] Büchner, and Joachim [Akademischer Betreuer] Wosnitza. "Physical Properties of Iron-based Superconductors Probed by Low-Temperature Specific-Heat Measurements / Mahmoud Mohamed. Gutachter: Bernd Büchner ; Joachim Wosnitza. Betreuer: Anja Wolter-Giraud." Dresden : Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2012. http://d-nb.info/1068148551/34.

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46

Yong, Jie. "Quantum Critical Behavior in Deeply Underdoped Cuprate Films and Pairing Symmetry in Iron Pnictide Superconductors Probed by Penetration Depth Measurements." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1337713622.

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Tomic, Milan [Verfasser], Roser [Akademischer Betreuer] Valenti, and Peter [Akademischer Betreuer] Hirschfeld. "Ab-initio simulations of pressure effects on structural and electronic properties of iron based superconductors / Milan Tomic. Gutachter: Roser Valentí ; Peter Hirschfeld. Betreuer: Roser Valentí." Frankfurt am Main : Univ.-Bibliothek Frankfurt am Main, 2015. http://d-nb.info/1067918175/34.

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Ammar, Kirmani A. "NOVEL PHYSICAL PHENOMENA IN CORRELATED SUPERFLUIDS AND SUPERCONDUCTORS IN- AND OUT-OF-EQUILIBRIUM." Kent State University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=kent1586785964148996.

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Ahn, Felix Wolfgang [Verfasser], Ilya [Gutachter] Eremin, and Konstantin [Gutachter] Efetov. "Effect of spin-orbit coupling and multi-orbital effects in the iron-based superconductors / Felix Wolfgang Ahn ; Gutachter: Ilya Eremin, Konstantin Efetov ; Fakultät für Physik und Astronomie." Bochum : Ruhr-Universität Bochum, 2018. http://d-nb.info/1150509988/34.

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Ahn, Felix [Verfasser], Ilya [Gutachter] Eremin, and Konstantin [Gutachter] Efetov. "Effect of spin-orbit coupling and multi-orbital effects in the iron-based superconductors / Felix Wolfgang Ahn ; Gutachter: Ilya Eremin, Konstantin Efetov ; Fakultät für Physik und Astronomie." Bochum : Ruhr-Universität Bochum, 2018. http://d-nb.info/1150509988/34.

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Dissertations / Theses on the topic 'Iron-based superconductors'

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