Relevant bibliographies by topics / Weyl fermion

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  1. Journal articles
  2. Dissertations / Theses
  3. Books
  4. Book chapters
  5. Conference papers
  6. Reports

Academic literature on the topic 'Weyl fermion'

Author: Grafiati
Published: 4 June 2021
Last updated: 6 February 2022

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Journal articles on the topic "Weyl fermion"

1

Xu, Su-Yang, Ilya Belopolski, Daniel S. Sanchez, Chenglong Zhang, Guoqing Chang, Cheng Guo, Guang Bian, et al. "Experimental discovery of a topological Weyl semimetal state in TaP." Science Advances 1, no. 10 (November 2015): e1501092. http://dx.doi.org/10.1126/sciadv.1501092.

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Weyl semimetals are expected to open up new horizons in physics and materials science because they provide the first realization of Weyl fermions and exhibit protected Fermi arc surface states. However, they had been found to be extremely rare in nature. Recently, a family of compounds, consisting of tantalum arsenide, tantalum phosphide (TaP), niobium arsenide, and niobium phosphide, was predicted as a Weyl semimetal candidates. We experimentally realize a Weyl semimetal state in TaP. Using photoemission spectroscopy, we directly observe the Weyl fermion cones and nodes in the bulk, and the Fermi arcs on the surface. Moreover, we find that the surface states show an unexpectedly rich structure, including both topological Fermi arcs and several topologically trivial closed contours in the vicinity of the Weyl points, which provides a promising platform to study the interplay between topological and trivial surface states on a Weyl semimetal’s surface. We directly demonstrate the bulk-boundary correspondence and establish the topologically nontrivial nature of the Weyl semimetal state in TaP, by resolving the net number of chiral edge modes on a closed path that encloses the Weyl node. This also provides, for the first time, an experimentally practical approach to demonstrating a bulk Weyl fermion from a surface state dispersion measured in photoemission.
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Ma, Tian-Chi, Jing-Nan Hu, Yuan Chen, Lei Shao, Xian-Ru Hu, and Jian-Bo Deng. "Coexistence of type-II and type-IV Dirac fermions in SrAgBi." Modern Physics Letters B 35, no. 11 (February 9, 2021): 2150181. http://dx.doi.org/10.1142/s0217984921501815.

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Relativistic massless Weyl and Dirac fermions have isotropic and linear dispersion relations to maintain Poincaré symmetry, which is the most basic symmetry in high-energy physics. The situation in condensed matter physics is less constrained; only certain subgroups of Poincaré symmetry — the 230 space groups that exist in 3D lattices — need be respected. Then, the free fermionic excitations that have no high-energy analogues could exist in solid state systems. Here, We discovered a type of nonlinear Dirac fermion without high-energy analogue in SrAgBi and named it type-IV Dirac fermion. The type-IV Dirac fermion has a nonlinear dispersion relationship and is similar to the type-II Dirac fermion, which has electron pocket and hole pocket. The effective model for the type-IV Dirac fermion is also found. It is worth pointing out that there is a type-II Dirac fermion near this new Dirac fermion. So we used two models to describe the coexistence of these two Dirac fermions. Topological surface states of these two Dirac points are also calculated. We envision that our findings will stimulate researchers to study novel physics of type-IV Dirac fermions, as well as the interplay of type-II and type-IV Dirac fermions.
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Chang, Guoqing, Su-Yang Xu, Daniel S. Sanchez, Shin-Ming Huang, Chi-Cheng Lee, Tay-Rong Chang, Guang Bian, et al. "A strongly robust type II Weyl fermion semimetal state in Ta3S2." Science Advances 2, no. 6 (June 2016): e1600295. http://dx.doi.org/10.1126/sciadv.1600295.

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Weyl semimetals are of great interest because they provide the first realization of the Weyl fermion, exhibit exotic quantum anomalies, and host Fermi arc surface states. The separation between Weyl nodes of opposite chirality gives a measure of the robustness of the Weyl semimetal state. To exploit the novel phenomena that arise from Weyl fermions in applications, it is crucially important to find robust separated Weyl nodes. We propose a methodology to design robust Weyl semimetals with well-separated Weyl nodes. Using this methodology as a guideline, we search among the material parameter space and identify by far the most robust and ideal Weyl semimetal candidate in the single-crystalline compound tantalum sulfide (Ta3S2) with new and novel properties beyond TaAs. Crucially, our results show that Ta3S2has the largestk-space separation between Weyl nodes among known Weyl semimetal candidates, which is about twice larger than the measured value in TaAs and 20 times larger than the predicted value in WTe2. Moreover, all Weyl nodes in Ta3S2are of type II. Therefore, Ta3S2is a type II Weyl semimetal. Furthermore, we predict that increasing the lattice by <4% can annihilate all Weyl nodes, driving a novel topological metal-to-insulator transition from a Weyl semimetal state to a topological insulator state. The robust type II Weyl semimetal state and the topological metal-to-insulator transition in Ta3S2are potentially useful in device applications. Our methodology can be generally applied to search for new Weyl semimetals.
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Lai, Hsin-Hua, Sarah E. Grefe, Silke Paschen, and Qimiao Si. "Weyl–Kondo semimetal in heavy-fermion systems." Proceedings of the National Academy of Sciences 115, no. 1 (December 18, 2017): 93–97. http://dx.doi.org/10.1073/pnas.1715851115.

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Insulating states can be topologically nontrivial, a well-established notion that is exemplified by the quantum Hall effect and topological insulators. By contrast, topological metals have not been experimentally evidenced until recently. In systems with strong correlations, they have yet to be identified. Heavy-fermion semimetals are a prototype of strongly correlated systems and, given their strong spin-orbit coupling, present a natural setting to make progress. Here, we advance a Weyl–Kondo semimetal phase in a periodic Anderson model on a noncentrosymmetric lattice. The quasiparticles near the Weyl nodes develop out of the Kondo effect, as do the surface states that feature Fermi arcs. We determine the key signatures of this phase, which are realized in the heavy-fermion semimetal Ce3Bi4Pd3. Our findings provide the much-needed theoretical foundation for the experimental search of topological metals with strong correlations and open up an avenue for systematic studies of such quantum phases that naturally entangle multiple degrees of freedom.
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ALONSO, J. L., J. L. CORTÉS, and E. RIVAS. "WEYL FERMION FUNCTIONAL INTEGRAL AND TWO-DIMENSIONAL GAUGE THEORIES." International Journal of Modern Physics A 05, no. 14 (July 20, 1990): 2839–51. http://dx.doi.org/10.1142/s0217751x90001331.

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In the path integral approach we introduce a general regularization scheme for a Weyl fermionic measure. This allows us to study the functional integral formulation of a two-dimensional U(1) gauge theory with an arbitrary content of left-handed and right-handed fermions. A particular result is that, in contrast with a regularization of the fermionic measure based on a unique Dirac operator, by taking the Dirac fermionic measure as a product of two independent Weyl fermionic measures a consistent and unitary result can be obtained for the Chiral Schwinger Model (CSM) as a byproduct of the arbitrariness in the definition of the fermionic measure.
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XU, YE-JUN, JUN SONG, HONG-CHUN YUAN, HONG-YI FAN, and QIU-YU LIU. "QUANTIZATION SCHEME FOR FERMIONIC SYSTEM AND s-ORDERED OPERATOR EXPANSION FORMULA OF FERMIONIC DENSITY OPERATORS." Modern Physics Letters A 26, no. 11 (April 10, 2011): 833–42. http://dx.doi.org/10.1142/s0217732311035213.

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We introduce the generalized fermionic Wigner operator with an s parameter. Based on its remarkable properties, we establish one-to-one mapping between fermion operators and their s-parametrized pseudo-classical correspondence, which may involve fermionic Weyl pseudo-classical correspondence, P-representation and Q-representation in a unified way. Furthermore, starting with the projector of the fermionic coherent state, we obtain the s-ordered operator expansion formula of fermionic density operators, which includes normally ordered, antinormally ordered and Weyl ordered product of operators for different values of s. Applications in calculating some Fermi operators' s-ordered expansions are presented.
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Xu, Bing, Zhenyao Fang, Miguel-Ángel Sánchez-Martínez, Jorn W. F. Venderbos, Zhuoliang Ni, Tian Qiu, Kaustuv Manna, et al. "Optical signatures of multifold fermions in the chiral topological semimetal CoSi." Proceedings of the National Academy of Sciences 117, no. 44 (October 19, 2020): 27104–10. http://dx.doi.org/10.1073/pnas.2010752117.

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We report the optical conductivity in high-quality crystals of the chiral topological semimetal CoSi, which hosts exotic quasiparticles known as multifold fermions. We find that the optical response is separated into several distinct regions as a function of frequency, each dominated by different types of quasiparticles. The low-frequency intraband response is captured by a narrow Drude peak from a high-mobility electron pocket of double Weyl quasiparticles, and the temperature dependence of the spectral weight is consistent with its Fermi velocity. By subtracting the low-frequency sharp Drude and phonon peaks at low temperatures, we reveal two intermediate quasilinear interband contributions separated by a kink at 0.2 eV. Using Wannier tight-binding models based on first-principle calculations, we link the optical conductivity above and below 0.2 eV to interband transitions near the double Weyl fermion and a threefold fermion, respectively. We analyze and determine the chemical potential relative to the energy of the threefold fermion, revealing the importance of transitions between a linearly dispersing band and a flat band. More strikingly, below 0.1 eV our data are best explained if spin-orbit coupling is included, suggesting that at these energies, the optical response is governed by transitions between a previously unobserved fourfold spin-3/2 node and a Weyl node. Our comprehensive combined experimental and theoretical study provides a way to resolve different types of multifold fermions in CoSi at different energy. More broadly, our results provide the necessary basis to interpret the burgeoning set of optical and transport experiments in chiral topological semimetals.
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Volovik, G. E., and M. A. Zubkov. "Emergent Weyl spinors in multi-fermion systems." Nuclear Physics B 881 (April 2014): 514–38. http://dx.doi.org/10.1016/j.nuclphysb.2014.02.018.

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Sukhachov, P. O. "Gap Generation in Weyl Semimetals in a Model with Local Four-Fermion Interaction." Ukrainian Journal of Physics 59, no. 7 (July 2014): 696–705. http://dx.doi.org/10.15407/ujpe59.07.0696.

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Huang, Shin-Ming, Su-Yang Xu, Ilya Belopolski, Chi-Cheng Lee, Guoqing Chang, Tay-Rong Chang, BaoKai Wang, et al. "New type of Weyl semimetal with quadratic double Weyl fermions." Proceedings of the National Academy of Sciences 113, no. 5 (January 19, 2016): 1180–85. http://dx.doi.org/10.1073/pnas.1514581113.

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Weyl semimetals have attracted worldwide attention due to their wide range of exotic properties predicted in theories. The experimental realization had remained elusive for a long time despite much effort. Very recently, the first Weyl semimetal has been discovered in an inversion-breaking, stoichiometric solid TaAs. So far, the TaAs class remains the only Weyl semimetal available in real materials. To facilitate the transition of Weyl semimetals from the realm of purely theoretical interest to the realm of experimental studies and device applications, it is of crucial importance to identify other robust candidates that are experimentally feasible to be realized. In this paper, we propose such a Weyl semimetal candidate in an inversion-breaking, stoichiometric compound strontium silicide, SrSi2, with many new and novel properties that are distinct from TaAs. We show that SrSi2 is a Weyl semimetal even without spin–orbit coupling and that, after the inclusion of spin–orbit coupling, two Weyl fermions stick together forming an exotic double Weyl fermion with quadratic dispersions and a higher chiral charge of ±2. Moreover, we find that the Weyl nodes with opposite charges are located at different energies due to the absence of mirror symmetry in SrSi2, paving the way for the realization of the chiral magnetic effect. Our systematic results not only identify a much-needed robust Weyl semimetal candidate but also open the door to new topological Weyl physics that is not possible in TaAs.
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Dissertations / Theses on the topic "Weyl fermion"

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Martelli, Riccardo. "On the trace anomaly of a Weyl fermion." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amslaurea.unibo.it/12060/.

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La seguente tesi si sviluppa in tre parti: un'introduzione alle simmetrie conformi e di scala, una parte centrale dedicata alle anomalie quantistiche ed una terza parte dedicata all'anomalia di traccia per fermioni. Nella seconda parte in particolare si introduce il metodo di calcolo alla Fujikawa e si discute la scelta di regolatori adeguati ed un metodo per ottenerli, si applicano poi questi metodi ai campi, scalare e vettoriale, per l'anomalia di traccia in spazio curvo. Nell'ultimo capitolo si calcolano le anomalie di traccia per un fermione di Dirac e per uno di Weyl; la motivazione per calcolare queste anomalie nasce dal fatto che recenti articoli hanno suggerito che possa emergere un termine immaginario proporzionale alle densità di Pontryagin nell'anomalia di Weyl. Noi non abbiamo trovato questo termine e il risultato è che l'anomalia di traccia risulta essere metà di quella per il caso di Dirac.
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Chiese, Luca. "Anomalies of a Weyl fermion in a gauge background." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amslaurea.unibo.it/23909/.

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In this thesis we study the anomalies of a Weyl fermion in an abelian gauge back- ground. It is well-know that this model has a chiral anomaly which breaks the gauge invariance and prevents a consistent quantization of the corresponding gauge theory. In addition, there is a trace anomaly, whose precise structure is the main focus of the present study. We describe a derivation of these anomalies in terms of Feynman diagrams computa- tion, using dimensional regularization and the Breitenlohner-Maison scheme for treating the chiral matrix γ5. The issue discussed here is analogous to the one present in the context of a Weyl fermion coupled to a gravitational background. In that case, there has been recently a debate about the presence or absence of a contribution of a parity-odd term in the trace anomaly. The coupling of the Weyl fermion to an abelian gauge field provides a simpler setting for discussing the possible presence or absence of a parity-odd term in the trace anomaly. Our final result indicates that parity-odd terms do not arise.
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Reho, Riccardo. "A higher derivative fermion model." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020. http://amslaurea.unibo.it/19852/.

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Nel presente elaborato studiamo un modello fermionico libero ed invariante di scala con derivate di ordine elevato. In particolare, controlliamo che la simmetria di scala sia estendibile all'intero gruppo conforme. Essendoci derivate di ordine più alto il modello non è unitario, ma costituisce un nuovo esempio di teoria conforme libera. Nelle prime sezioni riguardiamo la teoria generale del bosone libero, partendo dapprima con modelli semplici con derivate di ordine basso, per poi estenderci a dimensioni arbitrarie e derivate più alte. In questo modo illustriamo la tecnica che ci permette di ottenere un modello conforme da un modello invariante di scala, attraverso l'accoppiamento con la gravità e richiedendo l'ulteriore invarianza di Weyl. Se questo è possibile, il modello originale ammette certamente l'intera simmetria conforme, che emerge come generata dai vettori di Killing conformi. Nel modello scalare l'accoppiamento con la gravità necessita di nuovi termini nell'azione, indispensabili anche la teoria sia appunto invariante di Weyl. La costruzione di questi nuovi termini viene ripetuta per un particolare modello fermionico, con azione contenente l'operatore di Dirac al cubo, per il quale dimostriamo l'invarianza conforme. Tale modello descrive equazioni del moto con derivate al terzo ordine. Dal momento che l'invarianza di Weyl garantisce anche l'invarianza conforme, ci si aspetta che il tensore energia-impulso corrispondente sia a traccia nulla. Per ogni modello introdotto controlliamo sistematicamente che tale condizione sia verifiata, ed in particolar modo per il caso della teoria fermionica con operator di Dirac cubico, che rappresenta il contributo originale di questa tesi.
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Broccoli, Matteo. "On the trace anomaly of a Weyl fermion in a gauge background." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018. http://amslaurea.unibo.it/16408/.

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In this thesis we study the trace anomaly of a Weyl fermion in an abelian gauge background. We first introduce the topic of anomaly in Quantum Fields Theory and provide case studies of a global and a gauge anomaly. Then, we review the lagrangians of the Weyl fermion and Dirac fermion, the models that are the focus of our chiral and trace anomaly computations. Since we evaluate the anomalies using Pauli-Villars (PV) regularization, we present different PV masses and discuss the classical symmetries they break. We identify the differential operators that enter our regularization schemes and we review the method that we use to evaluate anomalies: we read them from the path integral à la Fujikawa and compute them with heat kernel formulas. Then, we evaluate the chiral and trace anomaly of the models we are interested in. The chiral anomaly is well studied in the literature and we reproduce the standard result. The trace anomaly is our original result and, although the presence of the chiral anomaly implies a breakdown of gauge invariance, we find that the trace anomaly can be cast in a gauge invariant form. The issue is analogous to the one recently discussed in the literature about a conjectured contribution of an odd-parity term to the trace anomaly of a Weyl fermion in curved backgrounds. With an abelian gauge background, this odd-parity term would be a Chern-Pontryagin density, that does not appear in our final results.
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Suchet, Daniel Léo. "Simulating the dynamics of harmonically trapped Weyl particles with cold atoms Simultaneous sub-Doppler laser cooling of fermionic 6Li and 40K on the D1 line : Theory and experiment Analog simulation of Weyl particles with cold atoms." Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066262.

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Au cours de ma thèse, j'ai travaillé à la construction de l'expérience Fermix, consacrée à l'étude d'un mélange de fermions (6Li-40K) à très basses températures où les effets quantiques sont prédominants. Nous présentons ici deux résultats principaux. Premièrement, nous avons développé une nouvelle méthode de refroidissement sub-Doppler qui tire parti de l'existence d'états noirs dans la raie optique D1. Cette mélasse grise permet d'atteindre une densité de l'espace des phases de 10⁻⁴, la valeur la plus élevée rapportée dans la littérature pour le refroidissement laser simultané des deux espèces. Grâce à cette étape, nous avons pu réaliser un gaz fortement dégénéré de 3x10⁵ atomes de 40K, répartis dans deux états de spins, à une température de 62 nK, soit 17% de la température de Fermi. D'autre part, nous introduisons une transformation canonique pour montrer l'équivalence formelle entre le comportement de particules ultra-relativistes sans interactions (particules de Weyl) dans un potentiel harmonique et celui de fermions froids confinés dans un piège quadrupolaire. Nous étudions expérimentalement, numériquement et théoriquement la relaxation de tels systèmes vers un état stationnaire, non-Botlzmanien, caractérisé par des températures effectives fortement anisotropes. Cette analogie permet également d'interpréter des propriétés caractéristiques des particules relativistes. Ainsi, nous montrons que le paradoxe de Klein est analogue aux pertes Majorana. Pour finir, nous proposons une étude théorique des interactions médiées à longue distance par un système en dimensions mixtes
During my PhD, I contributed to the design and construction of the Fermix experiment, dedicated to the study of a 6Li-40K fermionic mixture at ultra low temperatures. Our main results are twofold. First, we developed a new sub-Doppler laser cooling scheme, taking advantage of the existence of dark states in the D1 line of alkali atoms. This so-called \emph{grey molasses} allows for a phase space density up to 10⁻⁴, the highest value reported for the simultaneous laser cooling of those two species. The improvement due to this cooling step enabled the production of a quantum degenerate 40K gas in a dipole trap, with 3x10⁵ atoms in two spin states at 62 nK, corresponding to 17% of the Fermi temperature. Second, introducing a canonical mapping, we showed that non-interacting ultra-relativistic particles (Weyl fermions) in a harmonic trap can be simulated by cold fermions confined in a quadrupole potential. We study experimentally, numerically and theoretically the relaxation of these systems towards a steady state which can not be described by a Boltzman distribution, but rather presents strongly anisotropic effective temperatures. This analogy also allows us to translate fundamental properties of relativistic particles in the language of cold atoms. In particular, we demonstrate that the Klein paradox is equivalent to Majorana losses. Finally, we present a theoretical study of the long range interactions between particles confined in two 2D layers immersed in a 3D atomic cloud
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Huxtable, Barton Duane Simon Barry. "Absence of a Scott correction for the total binding energy of noninteracting fermions in a smooth potential well /." Diss., Pasadena, Calif. : California Institute of Technology, 1988. http://resolver.caltech.edu/CaltechETD:etd-09062005-101909.

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Kluftinger, Benjamin Gregor. "An experimental study of the Quasi-Fermi level separations in quantum well solar cells." Thesis, Imperial College London, 2000. http://hdl.handle.net/10044/1/8246.

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Ekahana, Sandy Adhitia. "Investigation of topological nodal semimetals through angle-resolved photoemission spectroscopy." Thesis, University of Oxford, 2018. http://ora.ox.ac.uk/objects/uuid:afed6156-7aa2-4ba9-afd1-af53d775494f.

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Nodal semimetals host either degenerate points (Dirac/Weyl points) or lines whose band topology in Brillouin zone can be classified either as trivial (normal nodal semimetals) or non trivial (topological nodal semimetals). This thesis investigates the electronic structure of two different categories of topological nodal semimetals probed by angleresolved photoemission spectroscopy (ARPES): The first material is Indium Bismuth (InBi). InBi is a semimetal with simple tetragonal structure with P4/nmm space group. This space group is predicted to host protected nodal lines along the perpendicular momentum direction at the high symmetry lines of the Brillouin zone boundary even under strong spin-orbit coupling (SOC) situation. As a semimetal with two heavy elements, InBi is a suitable candidate to test the prediction. The investigation by ARPES demonstrates not only that InBi hosts the nodal line in the presence of strong SOC, it also shows the signature of type-II Dirac crossing along the perpendicular momentum direction from the center of Brillouin zone. However, as the nodal line observed is trivial in nature, there is no exotic drumhead surface states observed in this material. This finding demonstrates that Dirac crossings can be protected in a non-symmorphic space group. The second material is NbIrTe4 which is a semimetal that breaks inversion symmetry predicted to host only four Weyl points. This simplest configuration is confirmed by the measurement from the top and bottom surface of NbIrTe4 showing only a pair of Fermi arcs each. Furthermore, it is found that the Fermi arc connectivity on the bottom surface experiences re-wiring as it evolves from Weyl points energy to the ARPES Fermi energy level. This change is attributed to the hybridisation between the surface and the bulk states as their projection lie within the vicinity of each other. The finding in this work demonstrates that although Fermi arcs are guaranteed in Weyl semimetals, their shape and connectivity are not protected and may be altered accordingly.
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Ekins-Daukes, Nicholas John. "An investigation into the efficiency enhancement of strained and strain-balanced quantum well solar cells." Thesis, Imperial College London, 2000. http://hdl.handle.net/10044/1/8093.

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Qiu, Lei. "Exploring 2D Metal-Insulator Transition in p-GaAs Quantum Well with High rs." Case Western Reserve University School of Graduate Studies / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=case1386337954.

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Books on the topic "Weyl fermion"

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Kachelriess, Michael. Fermions and the Dirac equation. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198802877.003.0008.

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Starting from the spinor representation of the Lorentz group,Weyl spinors and their transformation properties are derived. The Dirac equation and the properties of its solutions are discussed. Graßmann numbers and the gener-ating functional for fermions are introduced. Weyl and Majorana fermions are examined.
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Li, Y. Y., and J. F. Jia. Topological Superconductors and Majorana Fermions. Edited by A. V. Narlikar. Oxford University Press, 2017. http://dx.doi.org/10.1093/oxfordhb/9780198738169.013.6.

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This article discusses recent developments relating to the so-called topological superconductors (TSCs), which have a full pairing gap in the bulk and gapless surface states consisting of Majorana fermions (MFs). It first provides a background on topological superconductivity as a novel quantum state of matter before turning to topological insulators (TIs) and superconducting heterostructures, with particular emphasis on the vortices of such materials and the Majorana mode within a vortex. It also considers proposals for realizing TSCs by proximity effects through TI/SC heterostructures as well as experimental efforts to fabricate artificial TSCs using nanowires, superconducting junctions, and ferromagnetic atomic chains on superconductors.
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Rau, Jochen. Perfect Gas. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780199595068.003.0006.

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The perfect gas is perhaps the most prominent application of statistical mechanics and for this reason merits a chapter of its own. This chapter briefly reviews the quantum theory of many identical particles, in particular the distinction between bosons and fermions, and then develops the general theory of the perfect quantum gas. It considers a number of limits and special cases: the classical limit; the Fermi gas at low temperature; the Bose gas at low temperature which undergoes Bose–Einstein condensation; as well as black-body radiation. For the latter we derive the Stefan–Boltzmann law, the Planck distribution, and Wien’s displacement law. This chapter also discusses the effects of a possible internal dynamics of the constituent molecules on the thermodynamic properties of a gas. Finally, it extends the theory of the perfect gas to dilute solutions.
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Horing, Norman J. Morgenstern. Schwinger Action Principle and Variational Calculus. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198791942.003.0004.

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Chapter 4 introduces the Schwinger Action Principle, along with associated particle and potential sources. While the methods described here originally arose in the relativistic quantum field theory of elementary particle physics, they have also profoundly advanced our understanding of non-relativistic many-particle physics. The Schwinger Action Principle is a quantum-mechanical variational principle that closely parallels the Hamilton Principle of Least Action of classical mechanics, generalizing it to include the role of quantum operators as generalized coordinates and momenta. As such, it unifies all aspects of quantum theory, incorporating Hamilton equations of motion for those operators and the Heisenberg equation, as well as producing the canonical equal-time commutation/anticommutation relations. It yields dynamical coupled field equations for the creation and annihilation operators of the interacting many-body system by variational differentiation of the Hamiltonian with respect to the field operators. Also, equations for the development of matrix elements (underlying Green’s functions) are derived using variations with respect to particle and potential “sources” (and coupling strength). Variational calculus, involving impressed potentials, c-number coordinates and fields, also quantum operator coordinates and fields, is discussed in full detail. Attention is given to the introduction of fermion and boson particle sources and their use in variational calculus.
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Mann, Peter. Calculus of Variations. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198822370.003.0036.

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This chapter presents an introduction to linear algebra. Classical mechanics is best understood in the language of differential geometry, which itself requires a working knowledge of the key concepts in linear algebra. This chapter walks through the required knowledge from this broad discipline and guides the reader towards the goal of the next chapter, differential geometry. Topics discussed include vector spaces, linear maps, basis sets, cobases, inner products, tensors, wedge products and exterior algebra, as well as the axioms of vector space geometry. The chapter concludes with a brief discussion of Grassmann variables, which tend to crop up when classical fermionic fields are defined.
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Janssen, Ted, Gervais Chapuis, and Marc de Boissieu. Origin and stability. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198824442.003.0006.

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The origin of the stability of aperiodic systems is very difficult to answer. Often the terms ‘competitive forces’ or ‘frustration’ have been proposed as the origin of stability. The role of Fermi surfaces and Brillouin zone boundary have also been invoked. This chapter deals with the numerous attempts which have been proposed for a better understanding. First, the Landau theory of phase transition, which has often been applied to understand the stability of incommensurate and composite systems, is presented here. Various semi-microscopic models are also proposed, in particular the Frenkel–Kontorova and Frank–Van der Merwe models, as well as spin models. Phase diagrams have been calculated with some success with the ANNI and DIFFOUR models. For quasicrystals, only the simplest general features are found in model systems. For a better understanding, more complex calculations are required, using, for example, ab initio methods. The chapter also discusses electronic instabilities, charge-density systems, Hume–Rothery compounds, and the growth of quasicrystals.
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Horing, Norman J. Morgenstern. Random Phase Approximation Plasma Phenomenology, Semiclassical and Hydrodynamic Models; Electrodynamics. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198791942.003.0010.

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Chapter 10 reviews both homogeneous and inhomogeneous quantum plasma dielectric response phenomenology starting with the RPA polarizability ring diagram in terms of thermal Green’s functions, also energy eigenfunctions. The homogeneous dynamic, non-local inverse dielectric screening functions (K) are exhibited for 3D, 2D, and 1D, encompassing the non-local plasmon spectra and static shielding (e.g. Friedel oscillations and Debye-Thomas-Fermi shielding). The role of a quantizing magnetic field in K is reviewed. Analytically simpler models are described: the semiclassical and classical limits and the hydrodynamic model, including surface plasmons. Exchange and correlation energies are discussed. The van der Waals interaction of two neutral polarizable systems (e.g. physisorption) is described by their individual two-particle Green’s functions: It devolves upon the role of the dynamic, non-local plasma image potential due to screening. The inverse dielectric screening function K also plays a central role in energy loss spectroscopy. Chapter 10 introduces electromagnetic dyadic Green’s functions and the inverse dielectric tensor; also the RPA dynamic, non-local conductivity tensor with application to a planar quantum well. Kramers–Krönig relations are discussed. Determination of electromagnetic response of a compound nanostructure system having several nanostructured parts is discussed, with applications to a quantum well in bulk plasma and also to a superlattice, resulting in coupled plasmon spectra and polaritons.
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Mee, Nicholas. The Cosmic Mystery Tour. Oxford University Press, 2019. http://dx.doi.org/10.1093/oso/9780198831860.001.0001.

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The Cosmic Mystery Tour is a brief account of modern physics and astronomy presented in a broad historical and cultural context. The book is attractively illustrated and aimed at the general reader. Part I explores the laws of physics including general relativity, the structure of matter, quantum mechanics and the Standard Model of particle physics. It discusses recent discoveries such as gravitational waves and the project to construct LISA, a space-based gravitational wave detector, as well as unresolved issues such as the nature of dark matter. Part II begins by considering cosmology, the study of the universe as a whole and how we arrived at the theory of the Big Bang and the expanding universe. It looks at the remarkable objects within the universe such as red giants, white dwarfs, neutron stars and black holes, and considers the expected discoveries from new telescopes such as the Extremely Large Telescope in Chile, and the Event Horizon Telescope, currently aiming to image the supermassive black hole at the galactic centre. Part III considers the possibility of finding extraterrestrial life, from the speculations of science fiction authors to the ongoing search for alien civilizations known as SETI. Recent developments are discussed: space probes to the satellites of Jupiter and Saturn; the discovery of planets in other star systems; the citizen science project SETI@Home; Breakthrough Starshot, the project to develop technologies to send spacecraft to the stars. It also discusses the Fermi paradox which argues that we might actually be alone in the cosmos
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Book chapters on the topic "Weyl fermion"

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Mehdi, Salah, and N. Prudhon. "Translation of Harmonic Spinors and Interacting Weyl Fermions on Homogeneous Spaces." In Springer Proceedings in Mathematics & Statistics, 185–208. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-65181-1_7.

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Korol, A. M., N. V. Medvid, and S. I. Litvynchuk. "Transport Properties of the Dirac-Weyl Electrons Through the Graphene-Based Superlattice Modulated by the Fermi Velocity Barriers." In Springer Proceedings in Physics, 215–21. Cham: Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-18543-9_13.

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"WEYL QUANTIZATION OF FERMIONS." In Structural Aspects of Quantum Field Theory and Noncommutative Geometry, 1107–35. WORLD SCIENTIFIC, 2013. http://dx.doi.org/10.1142/9789814472708_0045.

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"WEYL QUANTIZATION OF FERMIONS." In Structural Aspects of Quantum Field Theory and Noncommutative Geometry, 1113–40. 2nd ed. WORLD SCIENTIFIC, 2021. http://dx.doi.org/10.1142/9789811237089_0045.

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"Surface Fermi Arcs." In Electronic Properties of Dirac and Weyl Semimetals, 155–96. WORLD SCIENTIFIC, 2021. http://dx.doi.org/10.1142/9789811207358_0005.

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Eckle, Hans-Peter. "Models of Strongly Interacting Quantum Matter." In Models of Quantum Matter, 241–420. Oxford University Press, 2019. http://dx.doi.org/10.1093/oso/9780199678839.003.0008.

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This chapter introduces a select number of models of strongly interacting quantum many-particle physics and examines their basic properties. These models represent Bosonic and Fermionic systems as well as systems where magnetic moments, i.e. spins, interact. The main selection criterion has been the existence of a variant of the model that is quantum integrable using Bethe ansatz methods. After studying the Bose fluid, the Landau Fermi liquid, and the one-dimensional concept of the Luttinger liquid, it reviews some of the major models of condensed matter theory, including the Hubbard model describing itinerant magnetism, the Heisenberg model describing localized magnetism, and the Kondo model describing the interaction of a magnetic impurity and band electrons. It also presents the Rabi model and some of its descendants in order to describe the interaction of light and quantum matter in quantum optics.
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Zinn-Justin, Jean. "Functional integration: From path to field integrals." In From Random Walks to Random Matrices, 13–34. Oxford University Press, 2019. http://dx.doi.org/10.1093/oso/9780198787754.003.0002.

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Chapter 2 is rather descriptive and introduces the notion of functional (path and field) integrals, for boson (the holomorphic formalism) as well as fermion systems (this necessitates the introduction of Grassmann integration) as they are used in physics. Prior to the second half of the twentieth century, the technical tools of theoretical physics were mainly differential or partial differential equations. However, when systematic investigations of large scale systems with quantum of statistical fluctuations began, new tools were required. This led to the development of functional integration. In this chapter, the role of Gaussian measures and Gaussian expectation values is emphasized, leading to Wick’s theorem, a tool for perturbative calculations. Functional integrals provide remarkable tools to study the classical limit and barrier penetration. They provide a simple bridge between non–relativistic quantum mechanics and quantum field theory.
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Weberszpil, José, and José Abdalla Helayël-Neto. "Revisiting Anomalous g-Factors for Charged Leptons in a Fractional Coarse-Grained Approach With Axiomatic Local Metric Derivatives." In Advanced Applications of Fractional Differential Operators to Science and Technology, 171–97. IGI Global, 2020. http://dx.doi.org/10.4018/978-1-7998-3122-8.ch008.

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This contribution sets out to extend the concept of helicity so as to include it in a fractional scenario with a low-level of fractionality. To accomplish this goal, the authors write down the left- and the right-handed Weyl equations from first principles in this extended framework. Next, by coupling the two different fractional Weyl sectors by means of a mass parameter, they arrive at the fractional version of Dirac's equation, which, whenever coupled to an external electromagnetic field and reduced to the non-relativistic regime, yields a fractional Pauli-type equation. From the latter, they are able to present an explicit expression for the gyromagnetic ratio of charged fermions in terms of the fractionality parameter. They then focus their efforts to relate the coarse-grained property of space-time to fractionality and to the (g-2) anomalies of the different leptonic species. To do this, they build up an axiomatic local metric derivative that exhibits the Mittag-Leffler function as eigenfunction and is valid for low-level fractionality, whenever the order parameter is close to 1.
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Schmickler, Wolfgang. "The semiconductor-electrolyte interface." In Interfacial Electrochemistry. Oxford University Press, 1996. http://dx.doi.org/10.1093/oso/9780195089325.003.0012.

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Many naturally occurring substances, in particular the oxide films that form spontaneously on some metals, are semiconductors. Also, electrochemical reactions are used in the production of semiconductor chips, and recently semiconductors have been used in the construction of electrochemical photocells. So there are good technological reasons to study the interface between a semiconductor and an electrolyte. Our main interest, however, lies in more fundamental questions: How does the electronic structure of the electrode influence the properties of the electrochemical interface, and how does it affect electrochemical reactions? What new processes can occur at semiconductors that are not known from metals? We begin by recapitulating a few facts about semiconductors. Electronic states in a perfect semiconductor are delocalized just as in metals, and there are bands of allowed electronic energies. According to a well-known theorem, bands that are either completely filled or completely empty do not contribute to the conductivity. In semiconductors the current-carrying bands do not overlap as they do in metals; they are separated by the band gap, and the Fermi level lies right in this gap. The band below the Fermi level, which at T = 0 is completely filled, is known as the valence band; the band above, which is empty at T = 0, is the conduction band. In a pure or intrinsic semiconductor, the Fermi level is close to the center of the band gap. At room temperature a few electrons are excited from the valence into the conduction band, leaving behind electron vacancies or holes (denoted by h+). The electric current is carried by electrons in the conduction band and holes in the valence band. The concentrations nc of the conduction electrons and pv of the holes are determined from Fermi statistics.
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Kolanoski, Hermann, and Norbert Wermes. "Semiconductor detectors." In Particle Detectors, 255–372. Oxford University Press, 2020. http://dx.doi.org/10.1093/oso/9780198858362.003.0008.

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Already since the early 1960s semiconductor detectors have been employed in nuclear physics, in particular for gamma ray energy measurement. This chapter concentrates on position sensitive semiconductor detectors which have been developed in particle physics since the 1980s and which feature position resolutions in the range of 50–100 μ‎m by structuring the electrodes, thus reaching the best position resolutions of electronic detectors. For the first time this made the electronic measurement of secondary vertices and therewith the lifetime of heavy fermions possible. The chapter first conveys the basics of semiconductor physics, of semiconductor and metal-semiconductor junctions used in electronics and detector applications as well as particle detection with semiconductor detectors. It follows the description of different detector types, like strip and pixel detectors, silicon drift chambers and charged-coupled devices. New developments are addressed in the sections on ‘Monolithic pixel detectors’ and on ‘Precision timing with silicon detectors’. In the last sections detector deterioration by radiation damage is described and an overview of other semiconductor detector materials but silicon is given.
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Conference papers on the topic "Weyl fermion"

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Nagaosa, Naoto. "Correlated Weyl Fermions in Oxides." In Proceedings of the International Conference on Strongly Correlated Electron Systems (SCES2019). Journal of the Physical Society of Japan, 2020. http://dx.doi.org/10.7566/jpscp.30.011007.

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Buividovich, P. V. "Surface states of massive Dirac fermions with separated Weyl nodes." In XITH CONFERENCE ON QUARK CONFINEMENT AND HADRON SPECTRUM. AIP Publishing LLC, 2016. http://dx.doi.org/10.1063/1.4938609.

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Kumar, Upendra, Vipin Kumar, Enamullah, and Girish S. Setlur. "Bloch-Siegert shift in Dirac-Weyl fermionic systems." In DAE SOLID STATE PHYSICS SYMPOSIUM 2017. Author(s), 2018. http://dx.doi.org/10.1063/1.5029045.

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Noh, Jiho, Sheng Huang, Daniel Leykam, Y. D. Chong, Kevin Chen, and Mikael C. Rechtsman. "Experimental observation of optical Weyl points and Fermi arcs." In CLEO: QELS_Fundamental Science. Washington, D.C.: OSA, 2017. http://dx.doi.org/10.1364/cleo_qels.2017.fm3g.3.

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Ajaykumar, Arjun, Zhou Xing, Binit Syamal, and Siau Ben Chiah. "Compact Fermi potential model for heterostructure HEMTs with rectangular quantum well." In ESSDERC 2014 - 44th European Solid State Device Research Conference. IEEE, 2014. http://dx.doi.org/10.1109/essderc.2014.6948811.

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Ghosh, Kunal, and Christiana Honsberg. "Absorption coefficient for Multiple-Quasi Fermi level system in quantum well." In 2011 37th IEEE Photovoltaic Specialists Conference (PVSC). IEEE, 2011. http://dx.doi.org/10.1109/pvsc.2011.6186486.

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Bulusu, A., and D. G. Walker. "Coupled Quantum-Scattering Madeling of Thermoelectric Properties of Si/Ge/Si Quantum Well Structures." In ASME 2006 International Mechanical Engineering Congress and Exposition. ASMEDC, 2006. http://dx.doi.org/10.1115/imece2006-15274.

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Confined structures presumably offer enhanced performance of thermoelectric devices. 1) Interfaces and boundaries create scattering sites for phonons, which reduces the thermal conductivity. 2) Reduced dimensionality increases the local density of states near the Fermi level, which increases the Seebeck coefficient. From these two phenomena, the net effect should be an increase in ZT, the performance parameter used to evaluate different materials and structures. These effects have been measured and modeled, but none of the models attempts to quantify the electron-phonon coupled effects particularly in the regime where quantum and scattering influences are found. Using the non-equilibrium Green's function (NEGF) approach, quantum wells composed of Si and Ge are studied and the important physics isolated. Results show a competing effect between the decrease in the electrical conductivity due to scattering with the increase in electrical conductivity with doping, leading to 77% decrease in the value of the power factor for the case of electron-optical phonon scattering.
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Inoue, Shuhei, Takeshi Nakajima, Kazuya Nomura, and Yoshihiro Kikuchi. "Selective Synthesis of Single-Walled Carbon Nanotubes by Blending Catalysts." In ASME/JSME 2007 Thermal Engineering Heat Transfer Summer Conference collocated with the ASME 2007 InterPACK Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/ht2007-32524.

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Single-walled carbon nanotubes are considered the most attractive material and a lot of synthesis processes are developed. Among these synthesis processes chemical vapor deposition processes are considered to be most suitable for macroscopic production. In many CVD processes the alcohol catalytic CVD process can be the best process because it can produce very pure nanotubes without any purification. However, cobalt is essential as a catalyst that makes the flexibility of catalysts restricted. In this paper, our investigation mainly focused on as follows: The efficiency of combined catalysts with/without cobalt. The diameter distributions against catalysts density. The electrical states of catalysts near Fermi level. Consequently, almost all of cobalt containing catalysts worked well, and the diameter distributions were proportional to the particle size. Efficient catalysts had enough states around Fermi level and the cobalt-less efficient catalyst cluster model showed the similar density of state to the cobalt cluster. Thus, noticing to the DOS, other efficient catalysts can be discovered and the diameter distribution will be controllable by adjusting temperature, a catalyst size, and a catalyst combination without any complicated techniques and facilities.
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Fitzpatrick, Gerard. "A search for long-lived emission from well-localized Fermi GBM GRBs using the Earth Occultation Technique." In 8th INTEGRAL Workshop “The Restless Gamma-ray Universe”. Trieste, Italy: Sissa Medialab, 2011. http://dx.doi.org/10.22323/1.115.0095.

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Gabbay, A., Yulia Preezant, E. Cohen, B. M. Ashkinadze, and L. N. Pfeiffer. "Polaritons composed of 2DEG Fermi-edge transitions in a GaAs/AlGaAs modulation doped quantum well embedded in a microcavity." In PHYSICS OF SEMICONDUCTORS: 28th International Conference on the Physics of Semiconductors - ICPS 2006. AIP, 2007. http://dx.doi.org/10.1063/1.2730291.

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Reports on the topic "Weyl fermion"

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Huang, Lunan. Studies of Dirac and Weyl fermions by angle resolved photoemission spectroscopy. Office of Scientific and Technical Information (OSTI), January 2016. http://dx.doi.org/10.2172/1342554.

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Riley, Mark, and Akis Pipidis. The Mechanical Analogue of the "Backbending" Phenomenon in Nuclear-structure Physics. Florida State University, May 2008. http://dx.doi.org/10.33009/fsu_physics-backbending.

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This short pedagogical movie illustrates an effect in nuclear physics called backbending which was first observed in the study of the rotational behavior of rapidly rotating rare-earth nuclei in Stockholm, Sweden in 1971. The video contains a mechanical analog utilizing rare-earth magnets and rotating gyroscopes on a turntable along with some historic spectra and papers associated with this landmark discovery together with its explanation in terms of the Coriolis induced uncoupling and rotational alignment of a specific pair of particles occupying high-j intruder orbitals. Thus backbending represents a crossing in energy of the groundstate, or vacuum, rotational band by another band which has two unpaired high-j nucleons (two quasi-particles) with their individual angular momenta aligned with the rotation axis of the rapidly rotating nucleus. Backbending was a major surprise which pushed the field of nuclear structure physics forward but which is now sufficiently well understood that it can be used as a precision spectroscopic tool providing useful insight for example, into nuclear pairing correlations and changes in the latter due to blocking effects and quasi-particle seniority, nuclear deformation, the excited configurations of particular rotational structures and the placement of proton and neutron intruder orbitals at the Fermi surface.
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