Journal articles: 'Spectroscopie à excitation de spin'

1

Loth, Sebastian, Christopher P. Lutz, and Andreas J. Heinrich. "Spin-polarized spin excitation spectroscopy." New Journal of Physics 12, no. 12 (December 22, 2010): 125021. http://dx.doi.org/10.1088/1367-2630/12/12/125021.

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Korshunov, Maxim M., Svetoslav A. Kuzmichev, and Tatiana E. Kuzmicheva. "Direct Observation of the Spin Exciton in Andreev Spectroscopy of Iron-Based Superconductors." Materials 15, no. 17 (September 3, 2022): 6120. http://dx.doi.org/10.3390/ma15176120.

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Quasiparticle excitations provide viable information on the physics of unconventional superconductors. Higgs and Leggett modes are some of the classic examples. Another important bosonic excitation is the spin exciton originating from the sign-changing superconducting gap structure. Here we report a direct observation of the temperature-dependent spin exciton in the Andreev spectra of iron-based superconductors. Combined with the other experimental evidence, our observation confirms the extended s-wave (s±) order parameter symmetry and indirectly proves the spin-fluctuation mechanism of Cooper pairing.

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Zvyagin, Sergei. "Spin Dynamics in Quantum Sine-Gordon Spin Chains: High-Field ESR Studies." Applied Magnetic Resonance 52, no. 4 (February 24, 2021): 337–48. http://dx.doi.org/10.1007/s00723-021-01310-9.

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AbstractA spin-1/2 Heisenberg antiferromagnetic chain is one of the most important paradigmatic models in quantum magnetism. Its ground state is a spin singlet, while the excitation spectrum is formed by gapless fractional excitations, spinons. The presence of alternating g-tensors and/or the staggered Dzyaloshinskii-Moriya interaction results in opening the energy gap $$\varDelta \propto H^{2/3}$$ Δ ∝ H 2 / 3 , once the magnetic field H is applied. A fairly good understanding of this phenomenon was achieved in the framework of the sine-Gordon quantum-field theory, taking into account the effective transverse staggered field induced by the applied uniform field. The theory predicts solitons and antisolitons as elementary excitations, as well as their bound states, breathers. Here, I review recent high-field electron spin resonance spectroscopy studies of such systems, focusing on peculiarities of their spin dynamics in the sine-Gordon regime and beyond.

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Geilen, Moritz, Alexandra Nicoloiu, Daniele Narducci, Morteza Mohseni, Moritz Bechberger, Milan Ender, Florin Ciubotaru, et al. "Fully resonant magneto-elastic spin-wave excitation by surface acoustic waves under conservation of energy and linear momentum." Applied Physics Letters 120, no. 24 (June 13, 2022): 242404. http://dx.doi.org/10.1063/5.0088924.

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We report on the resonant excitation of spin waves in micro-structured magnetic thin films by short-wavelength surface acoustic waves (SAWs). The spin waves as well as the acoustic waves are studied by micro-focused Brillouin light scattering spectroscopy. At low magnetic bias fields, a resonant phonon–magnon conversion is possible, which results in the excitation of short-wavelength spin waves. Using micromagnetic simulations, we verify that during this excitation both energy and linear momentum are conserved and fully transferred from the SAW to the spin wave. This conversion can already be detected after an interaction length of a few micrometers. Thus, our findings pave the way for miniaturized magneto-elastic spin-wave emitters for magnon computing.

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Senaratne, Ruwan, Danyel Cavazos-Cavazos, Sheng Wang, Feng He, Ya-Ting Chang, Aashish Kafle, Han Pu, Xi-Wen Guan, and Randall G. Hulet. "Spin-charge separation in a one-dimensional Fermi gas with tunable interactions." Science 376, no. 6599 (June 17, 2022): 1305–8. http://dx.doi.org/10.1126/science.abn1719.

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Ultracold atoms confined to periodic potentials have proven to be a powerful tool for quantum simulation of complex many-body systems. We confine fermions to one dimension to realize the Tomonaga-Luttinger liquid model, which describes the highly collective nature of their low-energy excitations. We use Bragg spectroscopy to directly excite either the spin or charge waves for various strengths of repulsive interaction. We observe that the velocity of the spin and charge excitations shift in opposite directions with increasing interaction, a hallmark of spin-charge separation. The excitation spectra are in quantitative agreement with the exact solution of the Yang-Gaudin model and the Tomonaga-Luttinger liquid theory. Furthermore, we identify effects of nonlinear corrections to this theory that arise from band curvature and back-scattering.

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FUKUOKA, DAISUKE, KOUSHIRO ARAHARA, TAKAAKI KOYAMA, NAOKI TANAKA, KENICHI OTO, KIYOFUMI MURO, SHOJIRO TAKEYAMA, GREGOSZ KARCZEWSKI, THOMASZ WOJTOWICZ, and JACEK KOSSUT. "COMPREHENSIVE STUDY OF SPIN-FLIP EXCITATIONS IN CdZnTe/CdZnMnTe QUANTUM WELLS." International Journal of Modern Physics B 21, no. 08n09 (April 10, 2007): 1610–14. http://dx.doi.org/10.1142/s0217979207043294.

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Spin-flip excitations in non-doped Cd 0.93 Zn 0.07 Te/Cd 0.48 Zn 0.04 Mn 0.48 Te quantum wells have been comprehensively studied by spin-flip Raman scattering (SFRS) spectroscopy and time-resolved Kerr rotation (TRKR) spectroscopy. In 4 nm quantum well, two spin-flip Raman peaks were observed in addition to the multiple Mn 2+ spin-flip scatterings. The spin-flip energies are isotropic against the magnetic field direction and well described by modified Brillouin functions. Based on the circumstantial analysis, they are assigned to the spin-flip of residual electrons and the electron spin-flip in the localized exciton, respectively, even though the large energy difference between the two electron spin-flip processes is a puzzle. While, in 9 nm quantum well a strange spin-flip excitation was observed together with a very weak Mn 2+ spin-flip scattering. The spin-flip energy changed strangely up to the magnetic field 4T, and then linearly increased with field (| g *|=1.15). A high-resolution TRKR spectroscopy revealed an unusual temperature dependence, which resembled "softening mode" of spin resonance observed in p-doped ferromagnetic CdMnTe quantum wells. However, these behaviors are well understood by an "inverted spin configuration", which results from a negative g*-factor and a very weak s-d interaction between the electrons and the manganese ions in the barrier.

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HOPSTER, H. "SPIN-POLARIZED ELECTRON ENERGY LOSS SPECTROSCOPY." Surface Review and Letters 01, no. 01 (June 1994): 89–96. http://dx.doi.org/10.1142/s0218625x94000114.

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Spin-polarized electron energy loss spectroscopy (SPEELS) probes the spin-dependent electron-hole pair excitation spectrum at surfaces. It is a very surface sensitive method for the detection of surface magnetization. Indirectly, information on surface magnetic moments is obtained. SPEELS is capable of resolving layer-by-layer antiferromagnetic order as found in 3d metal (Cr, Mn, V) films on Fe(100).

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Tait, Claudia E., and Stefan Stoll. "Coherent pump pulses in Double Electron Electron Resonance spectroscopy." Physical Chemistry Chemical Physics 18, no. 27 (2016): 18470–85. http://dx.doi.org/10.1039/c6cp03555h.

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9

Heng, Lai, and Huang Zhigao. "Spin-wave excitation and Mossbauer spectroscopy of amorphous alloys." Intermetallics 8, no. 5-6 (May 2000): 655–57. http://dx.doi.org/10.1016/s0966-9795(99)00136-3.

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10

Barkhuijsen, H., R. De Beer, B. J. Pronk, and D. Van Ormondt. "Partial excitation in electron spin-echo envelope modulation spectroscopy." Journal of Magnetic Resonance (1969) 61, no. 2 (February 1985): 284–93. http://dx.doi.org/10.1016/0022-2364(85)90083-6.

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11

Carlotto, Silvia, Mauro Sambi, Francesco Sedona, Andrea Vittadini, and Maurizio Casarin. "A Theoretical Study of the Occupied and Unoccupied Electronic Structure of High- and Intermediate-Spin Transition Metal Phthalocyaninato (Pc) Complexes: VPc, CrPc, MnPc, and FePc." Nanomaterials 11, no. 1 (December 28, 2020): 54. http://dx.doi.org/10.3390/nano11010054.

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The structural, electronic, and spectroscopic properties of high- and intermediate-spin transition metal phthalocyaninato complexes (MPc; M = V, Cr, Mn and Fe) have been theoretically investigated to look into the origin, symmetry and strength of the M–Pc bonding. DFT calculations coupled to the Ziegler’s extended transition state method and to an advanced charge density and bond order analysis allowed us to assess that the M–Pc bonding is dominated by σ interactions, with FePc having the strongest and most covalent M–Pc bond. According to experimental evidence, the lightest MPcs (VPc and CrPc) have a high-spin ground state (GS), while the MnPc and FePc GS spin is intermediate. Insights into the MPc unoccupied electronic structure have been gained by modelling M L2,3-edges X-ray absorption spectroscopy data from the literature through the exploitation of the current Density Functional Theory variant of the Restricted Open-Shell Configuration Interaction Singles (DFT/ROCIS) method. Besides the overall agreement between theory and experiment, the DFT/ROCIS results indicate that spectral features lying at the lowest excitation energies (EEs) are systematically generated by electronic states having the same GS spin multiplicity and involving M-based single electronic excitations; just as systematically, the L3-edge higher EE region of all the MPcs herein considered includes electronic states generated by metal-to-ligand-charge-transfer transitions involving the lowest-lying π* orbital (7eg) of the phthalocyaninato ligand.

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Teng, Lihua, Lijun Mu, and Xia Wang. "Spin-independent and spin-dependent re-excitation in CdZnTe studied by pump-probe spectroscopy." Physics Letters A 383, no. 27 (September 2019): 125851. http://dx.doi.org/10.1016/j.physleta.2019.125851.

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13

Hula, T., K. Schultheiss, F. J. T. Gonçalves, L. Körber, M. Bejarano, M. Copus, L. Flacke, et al. "Spin-wave frequency combs." Applied Physics Letters 121, no. 11 (September 12, 2022): 112404. http://dx.doi.org/10.1063/5.0090033.

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We experimentally demonstrate the generation of spin-wave frequency combs based on the nonlinear interaction of propagating spin waves in a microstructured waveguide. By means of time- and space-resolved Brillouin light scattering spectroscopy, we show that the simultaneous excitation of spin waves with different frequencies leads to a cascade of four-magnon scattering events, which ultimately results in well-defined frequency combs. Their spectral weight can be tuned by the choice of amplitude and frequency of the input signals. Furthermore, we introduce a model for stimulated four-magnon scattering, which describes the formation of spin-wave frequency combs in the frequency and time domain.

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14

Bañares, L., S. Skowronek, C. Perdiguero, and A. González Ureña. "Laser-Induced Charge Transfer Under Crossed-Beam Conditions: Application to the Na + I2 → Na+ + I2− System." Laser Chemistry 12, no. 1-2 (January 1, 1992): 33–42. http://dx.doi.org/10.1155/lc.12.33.

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A crossed-beam charge transfer study was carried out for the Na(32P3/2,1/2) + I2 → Na+ + I2− system using laser excitation of the Na atom. The excitation functions were measured for the title reaction, searching for spin orbit effects. A common energy threshold of E0≃0.23eV was found for both processes. In addition, similar post-threshold laws for each spin-orbit state indicate the absence of such effects over the low collision energy range.

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van Lierop, J., and D. H. Ryan. "Superparamagnetic Spin Dynamics Studied Using Selective Excitation Double Mössbauer Spectroscopy." Physical Review Letters 85, no. 14 (October 2, 2000): 3021–24. http://dx.doi.org/10.1103/physrevlett.85.3021.

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16

Enos, C. S., A. R. Lee, and A. G. Brenton. "Translational energy spectroscopy. Spin-conservation studies in collisional excitation processes." Rapid Communications in Mass Spectrometry 9, no. 5 (1995): 437–52. http://dx.doi.org/10.1002/rcm.1290090513.

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17

de Oliveira Santos, Francois. "Resonant Elastic Scattering." EPJ Web of Conferences 184 (2018): 01006. http://dx.doi.org/10.1051/epjconf/201818401006.

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Elastic scattering of nuclei at energies typically below 10 MeV/nucleon can be used as a powerful method for studying nuclear spectroscopy. Resonances are observed in the excitation function, corresponding to unbound states in the compound nucleus. The analysis of the shape of these resonances can provide the excitation energy, the total width, the partial width, and the spin of the excited states.

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18

Wiśniewski, J., W. Urban, T. Rząca-Urban, A. G. Smith, J. F. Smith, G. S. Simpson, I. Ahmad, and J. P. Greene. "Study of parity-doublet structure in the 147La nucleus." EPJ Web of Conferences 193 (2018): 05006. http://dx.doi.org/10.1051/epjconf/201819305006.

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The work reports several new excited states in the neutron-rich 147La nucleus, populated in spontaneous fission of 252Cf. The excitation scheme has been reinvestigated by means of γ-ray spectroscopy, using high-fold γ coincidences measured with the Gammasphere array of Ge detectors. It is shown that the 229.65-keV level has spin and parity 11/2-, which changes the 9/2- spin-parity reported in a recent evaluation and sets up the spinparity of the ground state as 5/2+. New levels allow to arrange the excitation scheme of 147La into a parity-doublet-like structure showing that the 147La nucleus may have an octupole deformation.

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19

Cao, Y., D. G. Mazzone, D. Meyers, J. P. Hill, X. Liu, S. Wall, and M. P. M. Dean. "Ultrafast dynamics of spin and orbital correlations in quantum materials: an energy- and momentum-resolved perspective." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 377, no. 2145 (April 2019): 20170480. http://dx.doi.org/10.1098/rsta.2017.0480.

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Many remarkable properties of quantum materials emerge from states with intricate coupling between the charge, spin and orbital degrees of freedom. Ultrafast photo-excitation of these materials holds great promise for understanding and controlling the properties of these states. Here, we introduce time-resolved resonant inelastic X-ray scattering (tr-RIXS) as a means of measuring the charge, spin and orbital excitations out of equilibrium. These excitations encode the correlations and interactions that determine the detailed properties of the states generated. After outlining the basic principles and instrumentations of tr-RIXS, we review our first observations of transient antiferromagnetic correlations in quasi two dimensions in a photo-excited Mott insulator and present possible future routes of this fast-developing technique. The increasing number of X-ray free electron laser facilities not only enables tackling long-standing fundamental scientific problems, but also promises to unleash novel inelastic X-ray scattering spectroscopies. This article is part of the theme issue ‘Measurement of ultrafast electronic and structural dynamics with X-rays’.

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Hoyos, M. A., T. Calderon, I. Vergara, and J. Garcia-Solé. "New structural and spectroscopic data for eosphorite." Mineralogical Magazine 57, no. 387 (June 1993): 329–36. http://dx.doi.org/10.1180/minmag.1993.057.387.16.

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AbstractX-ray diffraction refinement of the crystal structure of eosphorite has been carried out with reference to the orthorhombic space group Cmca. The structure is similar to that previously described by Hanson (1960), but the standard deviations are improved. Optical absorption and photoluminescence have also been studied for this mineral. Two sharp emission lines, denoted as R1 and R2, superimposed to a broad band (630-750 nm) have been related to the presence of Cr3+ ions. The excitation spectrum of these emissions confirms that the absorption (excitation) bands centred at 431 nm and 585 are related to with 4A2 → 4T1 and 4A2 → 4T2 spin allowed transitions of this ion.

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Seifert, Tom S., Stepan Kovarik, Dominik M. Juraschek, Nicola A. Spaldin, Pietro Gambardella, and Sebastian Stepanow. "Longitudinal and transverse electron paramagnetic resonance in a scanning tunneling microscope." Science Advances 6, no. 40 (September 2020): eabc5511. http://dx.doi.org/10.1126/sciadv.abc5511.

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Electron paramagnetic resonance (EPR) spectroscopy is widely used to characterize paramagnetic complexes. Recently, EPR combined with scanning tunneling microscopy (STM) achieved single-spin sensitivity with sub-angstrom spatial resolution. The excitation mechanism of EPR in STM, however, is broadly debated, raising concerns about widespread application of this technique. We present an extensive experimental study and modeling of EPR-STM of Fe and hydrogenated Ti atoms on a MgO surface. Our results support a piezoelectric coupling mechanism, in which the EPR species oscillate adiabatically in the inhomogeneous magnetic field of the STM tip. An analysis based on Bloch equations combined with atomic-multiplet calculations identifies different EPR driving forces. Specifically, transverse magnetic field gradients drive the spin-1/2 hydrogenated Ti, whereas longitudinal magnetic field gradients drive the spin-2 Fe. Also, our results highlight the potential of piezoelectric coupling to induce electric dipole moments, thereby broadening the scope of EPR-STM to nonpolar species and nonlinear excitation schemes.

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22

Du, Yuhan, Ju Chen, Wenbin Wu, Zeping Shi, Xianghao Meng, Cheng Zhang, Shijing Gong, Junhao Chu, and Xiang Yuan. "Comparative Raman spectroscopy of magnetic topological material EuCd₂X₂ (X = P, As)." Journal of Physics: Condensed Matter 34, no. 22 (March 30, 2022): 224001. http://dx.doi.org/10.1088/1361-648x/ac5d1b.

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Abstract EuCd2X2 (X = P, As) is a new class of magnetic topological materials discovered recently. The electronic structure and the band topology are intimately coupled with its magnetism, giving rise to interesting properties such as spin fluctuation and colossal magnetoresistance. Phonon excitation can contribute to the quasi-particle response of the topological matters through spin-lattice and electron–phonon coupling. However, the phonon properties of this material family remain unexplored. Here we report a comparative study of Raman-active vibration modes in EuCd2X2 (X = P, As) by means of angle-resolved, temperature-resolved, and magnetic-field-resolved Raman spectroscopy together with the first-principle calculations and Raman tensor analysis. The phonon properties can be tuned by chemical potential and temperature within the material family. All the phonon modes are softened with increased chemical pressure by replacing P with As. Angle-resolved polarized Raman spectroscopy reveals the configuration-sensitive Raman activity and the isotropic intensity response. In addition, the magneto-Raman spectrum indicates the stability of Raman-active vibration modes against the magnetic field at room temperature. Our work sheds light on the phonon dynamics of magnetic topological matters, which are potentially coupled with the topological charge and spin excitation.

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23

Frietsch, B., A. Donges, R. Carley, M. Teichmann, J. Bowlan, K. Döbrich, K. Carva, et al. "The role of ultrafast magnon generation in the magnetization dynamics of rare-earth metals." Science Advances 6, no. 39 (September 2020): eabb1601. http://dx.doi.org/10.1126/sciadv.abb1601.

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Ultrafast demagnetization of rare-earth metals is distinct from that of 3d ferromagnets, as rare-earth magnetism is dominated by localized 4f electrons that cannot be directly excited by an optical laser pulse. Their demagnetization must involve excitation of magnons, driven either through exchange coupling between the 5d6s-itinerant and 4f-localized electrons or by coupling of 4f spins to lattice excitations. Here, we disentangle the ultrafast dynamics of 5d6s and 4f magnetic moments in terbium metal by time-resolved photoemission spectroscopy. We show that the demagnetization time of the Tb 4f magnetic moments of 400 fs is set by 4f spin–lattice coupling. This is experimentally evidenced by a comparison to ferromagnetic gadolinium and supported by orbital-resolved spin dynamics simulations. Our findings establish coupling of the 4f spins to the lattice via the orbital momentum as an essential mechanism driving magnetization dynamics via ultrafast magnon generation in technically relevant materials with strong magnetic anisotropy.

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Plekhanov, Vladimir G., Vyacheslav F. Myshkin, Valery A. Khan, and Dmitry A. Izhoykin. "Manifestation of the Spin in the Isotope Effects." Advanced Materials Research 1084 (January 2015): 147–51. http://dx.doi.org/10.4028/www.scientific.net/amr.1084.147.

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Modern physics distinguishes three fundamental properties of atomic nuclei: mass; spin and related magnetic moment; volume (surrounding field strength), which are the source of isotope effects. The experiments showed that the isotope substitution of the light isotope with the hard one increased the band-to-band transition energy Eg, as well as the exciton binding energy Ebboth in semiconductors and insulators. The representative manifestation of the spin has been observed in photoluminescence excitation spectroscopy in highly enriched28Si crystals with shallow donor P, as well as in the separation of13C and12С isotope in magnetic field.

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Zerdane, S., L. Wilbraham, M. Cammarata, O. Iasco, E. Rivière, M. L. Boillot, I. Ciofini, and E. Collet. "Comparison of structural dynamics and coherence of d–d and MLCT light-induced spin state trapping." Chemical Science 8, no. 7 (2017): 4978–86. http://dx.doi.org/10.1039/c6sc05624e.

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TSOI, M. "CURRENT-DRIVEN MAGNONS IN MAGNETIC MULTILAYERS." International Journal of Modern Physics B 16, no. 20n22 (August 30, 2002): 2957. http://dx.doi.org/10.1142/s0217979202013298.

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Spin waves, or magnons, are intrinsic excitations in magnetic materials and have attracted considerable attention since introduced by Bloch in 1930.1 Recently ideas of spintronics have impacted this field dramatically. Berger2 and Sloczewski3 introduced completely new aspects of the physics of metallic ferromagnets in the presence of an electric current of high density. Excitation of magnons by an electric current has been predicted and seen in magnetic multilayers,4-6 where the driving force for the excitations is the spin-momentum transfer associated with an electric current flow. We have developed a microcontact technique (magnetic microcontact spectroscopy) to investigate the current-driven magnon generation.4,5 In our experiments we inject current densities as high as 109 A/cm2 into a Co/Cu multi-layer through a point contact made using a sharpened Ag wire carefully brought into contact with a multi-layer file. We observe current-driven magnons in multi-layers with both ferromagnetic4,5 and antiferromagnetic7 configuration of the adjacent layer magnetizations. Some further interesting applications of the technique, particularly, for studying fluctuation phenomena, resonant magnon generation, acoustic wave generation, etc., will be presented.

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Laoutaris, A., I. Madesis, E. P. Benis, and T. J. M. Zouros. "Production of C4+ (2s2p 3,1P) hollow states in collisions of 6-18 MeV C4+ (1s2, 1s2s 3S) mixed-state beams with gas targets." HNPS Proceedings 26 (April 1, 2019): 133. http://dx.doi.org/10.12681/hnps.1808.

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Normalized electron yields of the formation of 2s2p 3,1P states from the metastable states 1s2s 3,1S and from the ground state 1s21S were obtained in 6-18MeV C4+ collisions with H2, He, Ne and Ar gas targets. The method of zero-degree Auger projectile spectroscopy was used to detect electrons emitted in the Auger decay C4+ (2s2p 3,1P) → C5+ (1s) + e-with high resolution. These states are of particular importance in the detailed study of fundamental excitation mechanisms, i.e. electron-nucleus excitation, electron-electron excitation and electron-electron excitation with spin exchange. Currently, the role of the above mechanisms in the production of the 2s2p 3,1P states is investigated utilizing variable 1s2s 3S metastable fraction beams as a function of collision energy and target species. Our latest results are presented.

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Ползикова, Н. И., С. Г. Алексеев, В. А. Лузанов, and А. О. Раевский. "Электроакустическое возбуждение спиновых волн и их детектирование за счет обратного спинового эффекта Холла." Физика твердого тела 60, no. 11 (2018): 2170. http://dx.doi.org/10.21883/ftt.2018.11.46659.17nn.

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Abstract —In this paper, we present theoretical and experimental results on the excitation and detection of spin waves and spin currents in multifrequency bulk acoustic wave resonators containing iron–yttrium garnet (YIG) films in contact with the Pt film. Acoustically excited magnetic precession under the resonator conditions was established to produce spin pumping that also has a resonance character. A significant asymmetry in the frequency dependence of the voltage signal detected on the Pt film is revealed with respect to the frequency of the magnetoelastic resonance and is confirmed by theoretical calculations. Acoustic resonator spectroscopy in combination with the electric detection of magnetic dynamics using the inverse spin Hall effect is shown to be of interest for studying the dispersion of spin waves, as well as magnetic and magnetoelastic parameters of ferromagnetic films.

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Rommel, E., and R. Kimmich. "Slice excitation and localized NMR spectroscopy on the basis of spin locking." Journal of Magnetic Resonance (1969) 83, no. 2 (June 1989): 299–308. http://dx.doi.org/10.1016/0022-2364(89)90192-3.

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30

Zhu, Boxing, Jingwang Gu, Chunting Yu, Zengjun Xiao, Yang Chen, and Dongfeng Zhao. "High-resolution laser spectroscopy of the linear SiC2Si molecule and its astrophysical implications." Astronomy & Astrophysics 637 (May 2020): A81. http://dx.doi.org/10.1051/0004-6361/202037448.

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Small silicon-carbon clusters are important gas-phase constituents of stellar atmospheres, and are thought to play a role as potential seeds of the interstellar dusts formed in the envelopes of evolved carbon stars. Here we present the high-resolution optical spectra of the linear SiC2Si molecule (l-Si2C2) studied via laboratory experiments. The l-Si2C2 molecules are generated in a supersonically expanding planar plasma by discharging a silane-acetylene-argon gas mixture. The optical absorption spectra in the 5000−5300 Å region are recorded using sensitive pulsed cavity ring-down spectroscopy. In total, five optical absorption bands belonging to the $ \tilde{C} ^{3}\Sigma_{u} ^{-} $ – $ \tilde{X} ^{3}\Sigma_{g} ^{-} $ electronic transition system of l-Si2C2 are measured with fully resolved spin splitting fine structures in individual rotational transitions. Accurate spectroscopic constants for both $ \tilde{X} ^{3}\Sigma_{g} ^{-} $ and $ \tilde{C} ^{3}\Sigma_{u} ^{-} $ states of l-Si2C2, including the spin-spin interaction constants and spin-rotation interaction constants, are determined from the experimental spectra, which can be used to simulate these optical bands with different temperatures. Using the determined spectroscopic constants, optical spectra of l-Si2C2 simulated with different rotational excitation temperatures are compared to the stellar spectra of evolved carbon stars V Hya and IRAS 12311−23509, where the triatomic SiC2 are known to be abundant. Tentative assignments of the l-Si2C2 spectral features in the stellar spectra are discussed.

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Полтавцев, С. В., И. А. Югова, И. А. Акимов, Д. Р. Яковлев, and M. Bayer. "Фотонное эхо на локализованных экситонах в полупроводниковых наноструктурах." Физика твердого тела 60, no. 8 (2018): 1587. http://dx.doi.org/10.21883/ftt.2018.08.46254.17gr.

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AbstractAn overview on photon echo spectroscopy under resonant excitation of the exciton complexes in semiconductor nanostructures is presented. The use of four-wave-mixing technique with the pulsed excitation and heterodyne detection allowed us to measure the coherent response of the system with the picosecond time resolution. It is shown that, for resonant selective pulsed excitation of the localized exciton complexes, the coherent signal is represented by the photon echoes due to the inhomogeneous broadening of the optical transitions. In case of resonant excitation of the trions or donor-bound excitons, the Zeeman splitting of the resident electron ground state levels under the applied transverse magnetic field results in quantum beats of photon echo amplitude at the Larmor precession frequency. Application of magnetic field makes it possible to transfer coherently the optical excitation into the spin ensemble of the resident electrons and to observe a long-lived photon echo signal. The described technique can be used as a high-resolution spectroscopy of the energy splittings in the ground state of the system. Next, we consider the Rabi oscillations and their damping under excitation with intensive optical pulses for the excitons complexes with a different degree of localization. It is shown that damping of the echo signal with increase of the excitation pulse intensity is strongly manifested for excitons, while on trions and donor-bound excitons this effect is substantially weaker.

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Zhou, Kaiyuan, Lina Chen, Kequn Chi, Qingwei Fu, Zui Tao, Like Liang, Zhenyu Gao, et al. "Current-driven magnetization dynamics and its correlation with magnetization configurations in perpendicularly magnetized tunnel junctions." Journal of Applied Physics 132, no. 17 (November 7, 2022): 173906. http://dx.doi.org/10.1063/5.0107569.

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We study spin-transfer-torque-driven magnetization dynamics of a perpendicular magnetic tunnel junction nanopillar. Through the combined investigations on spin-torque ferromagnetic resonance and microwave spectroscopy, it is found that the free layer (FL) and the weak pinned reference layer (RL) exhibit distinct dynamic behaviors. First, frequency vs field dispersion for the FL and RL shows an opposite trend as the field varies. Second, the FL can support a single spin-wave (SW) mode for both parallel and antiparallel configurations, while the RL exhibits spin-wave excitation only for the antiparallel state. Those two SW modes coexist at the antiparallel state, and their oscillation frequency exhibits a crossover phenomenon with increasing the external magnetic field, which could be helpful in the mutual synchronization of auto-oscillations for SW-based neuromorphic computing.

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FURIS, MADALINA, TODD BARRICK, PATRICK ROBBINS, SCOTT A. CROOKER, MELISSA PETRUSKA, VICTOR KLIMOV, and Al L. EFROS. "EXCITON SPIN STATES IN NANOCRYSTAL QUANTUM DOTS REVEALED BY SPIN-POLARIZED RESONANT PHOTOLUMINESCENCE AND RAMAN SPECTROSCOPY." International Journal of Modern Physics B 18, no. 27n29 (November 30, 2004): 3769–74. http://dx.doi.org/10.1142/s0217979204027438.

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We performed spin-polarized resonant Raman and resonant photoluminescence excitation spectroscopy (also known as "fluorescence line narrowing") on ZnS -capped CdSe nanocrystal quantum dots in high magnetic fields to 33 Tesla and temperatures down to 1.7K, which allows detailed investigation of the excitonic spin states. In these experiments, spin-polarized electrons and holes are resonantly injected by circularly polarized light into colloidal quantum dots of specific size, using a narrowband tunable dye laser and a fiber-coupled probe that is specially-designed for use in high-field magnets. In addition to the expected broad features associated with excitonic recombination and Raman-like peaks associated with quantized acoustic phonons, the photoluminescence spectra measured at magnetic fields larger than 10 Tesla develop a sharp peak, which moves roughly linearly with applied magnetic field. Further, the energy of this high-field peak varies systematically as a function of nanocrystal size. However, unlike typical electron spin flip transitions, the mode energy extrapolates to a finite value at zero magnetic field, suggesting the existence of an additional size-dependent exchange mechanism.

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Dinh, Nguyen Nang, Le Ha Chi, Tran Thi Chung Thuy, and Thien Phap Nguyen. "Spectroscopic and Photoluminescent Properties of Nanostructured Polyfluorenes/TiO₂ Composite Films used for OLEDs." Communications in Physics 21, no. 1 (March 31, 2011): 51. http://dx.doi.org/10.15625/0868-3166/21/1/93.

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In this work we present spectroscopic and photoluminescent properties of nanostructured polymeric composite films of nanocrystalline TiO2 and polyfuorenes (PF+nc-TiO2). The films were deposited onto glass and KBr substrates by spin-coating PF-in-toluene solution with embedding of 5-nm thick nc-TiO2 particles. The nc-TiO2 wt concentration embedded in PF was chosen as 1%, 2% and 4%. The FTIR, FTR, UV-VIS-NIR and photoluminescence characterization were carried-out to study the influence of oxide nanoparticles on the absorption spectra, molecular structures and emissive luminescence of the composites. It was shown that the presence of TiO2 nanoparticles results in improvement of charge separation of carriers generated by light excitation. Under a short wavelength excitation, in some samples a PL enhancement was observed. Under normal or long wavelength excitation, PF fluorescence quenching occurred for all the composites. Aging process of the composites was also investigated.

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Xu, Zhen, Jing Liu, Shimin Hou, and Yongfeng Wang. "Manipulation of Molecular Spin State on Surfaces Studied by Scanning Tunneling Microscopy." Nanomaterials 10, no. 12 (November 30, 2020): 2393. http://dx.doi.org/10.3390/nano10122393.

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The adsorbed magnetic molecules with tunable spin states have drawn wide attention for their immense potential in the emerging fields of molecular spintronics and quantum computing. One of the key issues toward their application is the efficient controlling of their spin state. This review briefly summarizes the recent progress in the field of molecular spin state manipulation on surfaces. We focus on the molecular spins originated from the unpaired electrons of which the Kondo effect and spin excitation can be detected by scanning tunneling microscopy and spectroscopy (STM and STS). Studies of the molecular spin-carriers in three categories are overviewed, i.e., the ones solely composed of main group elements, the ones comprising 3d-metals, and the ones comprising 4f-metals. Several frequently used strategies for tuning molecular spin state are exemplified, including chemical reactions, reversible atomic/molecular chemisorption, and STM-tip manipulations. The summary of the successful case studies of molecular spin state manipulation may not only facilitate the fundamental understanding of molecular magnetism and spintronics but also inspire the design of the molecule-based spintronic devices and materials.

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Hu, Shengmin, Jialiang Ye, Ruiqi Liu, and Xinhui Zhang. "Valley dynamics of different excitonic states in monolayer WSe₂ grown by molecular beam epitaxy." Journal of Semiconductors 43, no. 8 (August 1, 2022): 082001. http://dx.doi.org/10.1088/1674-4926/43/8/082001.

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Abstract Monolayer transition-metal dichalcogenides possess rich excitonic physics and unique valley-contrasting optical selection rule, and offer a great platform for long spin/valley lifetime engineering and the associated spin/valleytronics exploration. Using two-color time-resolved Kerr rotation and time-resolved reflectivity spectroscopy, we investigate the spin/valley dynamics of different excitonic states in monolayer WSe2 grown by molecular beam epitaxy. With fine tuning of the photon energy of both pump and probe beams, the valley relaxation process for the neutral excitons and trions is found to be remarkably different—their characteristic spin/valley lifetimes vary from picoseconds to nanoseconds, respectively. The observed long trion spin lifetime of > 2.0 ns is discussed to be associated with the dark trion states, which is evidenced by the photon-energy dependent valley polarization relaxation. Our results also reveal that valley depolarization for these different excitonic states is intimately connected with the strong Coulomb interaction when the optical excitation energy is above the exciton resonance.

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Martyshkin A.A., Beginin E. N., Sheshukova S.E., Sharaevsky Yu. P., Nikitov S.A., and Sadovnikov A.V. "Peculiarities of the formation of band gaps in mul-timode regime of spin waves propagation in mag-nonic crystals." Physics of the Solid State 64, no. 9 (2022): 1269. http://dx.doi.org/10.21883/pss.2022.09.54164.17hh.

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The dynamics of spin waves during their multimode propagation in a magnonic crystal, which is an irregular narrow ferrite waveguide with periodic boundary modulation, has been studied by the method of Mandelstam--Brillouin spectroscopy. The transformation of the mode composition of spin waves propagating in an irregular ferrite waveguide is shown. The space-time dynamics of spin waves and the characteristics of the band gaps of a magnonic crystal are experimentally studied, and the possibility of controlling the frequency-selective properties of such a structure is shown. By excitation of a superposition of even or odd width modes of the ferrite microstructure, it becomes possible to control the position of the band gaps of a magnonic crystal. The results of the experiment agree with the results of micromagnetic modeling of the propagation and transformation of the spectrum of spin waves propagating in a ferromagnetic periodic structure. Keywords: spin waves, magnonics, magnonic crystal, micromagnetic modeling.

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BUCURESCU, D., I. CĂTA-DANIL, M. IVAŞCU, N. MĂRGINEAN, L. STROE, C. A. UR, and N. DINU. "LIFETIMES AND STRUCTURE OF EXCITED STATES OF 73AS." International Journal of Modern Physics E 08, no. 01 (February 1999): 17–38. http://dx.doi.org/10.1142/s0218301399000045.

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The lifetimes of twelve low spin excited states in 73 As , below 2 MeV excitation, have been measured with the DSA method in the 73 Ge ( p , n γ) reaction. The existing data (energy levels, electromagnetic moments, transition probabilities and branching ratios, one-nucleon transfer spectroscopic factors) are discussed in the frame of multi-shell interacting boson-fermion model calculations. A good agreement is obtained for a large number of levels.

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Ignatyeva, Daria O., and Vladimir I. Belotelov. "Magneto-Optical Spectroscopy of Short Spin Waves by All-Dielectric Metasurface." Nanomaterials 12, no. 23 (November 25, 2022): 4180. http://dx.doi.org/10.3390/nano12234180.

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The optical method of spin dynamics measurements via the detection of various magneto-optical effects is widely used nowadays. Besides it being a convenient method to achieve time-resolved measurements, its spatial resolution in the lateral direction is limited by a diffraction limit for the probe light. We propose a novel approach utilizing a Mie-resonance-based all-dielectric metasurface that allows for the extraction of a signal of a single submicron-wavelength spin wave from the wide spin precession spectra. This approach is based on the possibility of designing a metasurface that possesses nonuniform magneto-optical sensitivity to the different nanoscale regions of the smooth magnetic film due to the excitation of the Mie modes. The metasurface is tuned to be unsensitive to the long-wavelength spin precession, which is achieved by the optical resonance-caused zeroing of the magneto-optical effect for uniform magnetization in the vicinity of the resonance. At the same time, such a Mie-supporting metasurface exhibits selective sensitivity to a narrow range of short wavelengths equal to its period.

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40

Kuz’min, V. S., and V. M. Kolesenko. "Resonant excitation of single-pulse nuclear spin echo in magnetically ordered media." Journal of Applied Spectroscopy 76, no. 3 (May 2009): 362–69. http://dx.doi.org/10.1007/s10812-009-9185-z.

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Kirschner, J., and S. Suga. "Spin-polarized electron energy-loss spectroscopy and the stoner excitation spectrum of iron." Surface Science Letters 178, no. 1-3 (December 1986): A651. http://dx.doi.org/10.1016/0167-2584(86)90156-8.

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Li, Geng-Ying, Yu Jiang, and Xue-Wen Wu. "Composite pulse excitation for spin-1 pure nuclear quadrupole resonance spectroscopy in powders." Chemical Physics Letters 202, no. 1-2 (1993): 82–86. http://dx.doi.org/10.1016/0009-2614(93)85354-q.

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43

Kirschner, J., and S. Suga. "Spin-polarized electron energy-loss spectroscopy and the stoner excitation spectrum of iron." Surface Science 178, no. 1-3 (December 1986): 327–35. http://dx.doi.org/10.1016/0039-6028(86)90308-0.

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44

Hassan, Ali, Abbas Ahmad Khan, Yeong Hwan Ahn, Muhammad Azam, Muhammad Zubair, Wei Xue, and Yu Cao. "Orientation-Mediated Luminescence Enhancement and Spin-Orbit Coupling in ZnO Single Crystals." Nanomaterials 12, no. 13 (June 26, 2022): 2192. http://dx.doi.org/10.3390/nano12132192.

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Temperature-, excitation wavelength-, and excitation power-dependent photoluminescence (PL) spectroscopy have been utilized to investigate the orientation-modulated near band edge emission (NBE) and deep level emission (DLE) of ZnO single crystals (SCs). The near-band-edge emission of ZnO SC with <0001> orientation exhibits strong and sharp emission intensity with suppressed deep level defects (mostly caused by oxygen vacancies Vo). Furthermore, Raman analysis reveals that <0001> orientation has dominant E2 (high) and E2 (low) modes, indicating that this direction has better crystallinity. At low temperature, the neutral donor-to-bound exciton (DoX) transition dominates, regardless of the orientation, according to the temperature-dependent PL spectra. Moreover, free-exciton (FX) transition emerges at higher temperatures in all orientations. The PL intensity dependence on the excitation power has been described in terms of power-law (I~Lα). Our results demonstrate that the α for <0001>, <1120>, and <1010> is (1.148), (1.180), and (1.184) respectively. In short, the comprehensive PL analysis suggests that DoX transitions are dominant in the NBE region, whereas oxygen vacancies (Vo) are the dominant deep levels in ZnO. In addition, the <0001> orientation contains fewer Vo-related defects with intense excitonic emission in the near band edge region than other counterparts, even at high temperature (~543 K). These results indicate that <0001> growth direction is favorable for fabricating ZnO-based highly efficient optoelectronic devices.

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45

Ginthör, Stephan J., Judith Schlagnitweit, Matthias Bechmann, and Norbert Müller. "Nuclear spin noise tomography in three dimensions with iterative simultaneous algebraic reconstruction technique (SART) processing." Magnetic Resonance 1, no. 2 (August 6, 2020): 165–73. http://dx.doi.org/10.5194/mr-1-165-2020.

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Abstract. We report three-dimensional spin noise imaging (SNI) of nuclear spin density from spin noise data acquired by Faraday detection. Our approach substantially extends and improves the two-dimensional SNI method for excitation-less magnetic resonance tomography reported earlier (Müller and Jerschow, 2006). This proof of principle was achieved by taking advantage of the particular continuous nature of spin noise acquired in the presence of constant magnitude magnetic field gradients and recent advances in nuclear spin noise spectroscopy acquisition as well as novel processing techniques. In this type of projection–reconstruction-based spin noise imaging the trade-off between signal-to-noise ratio (or image contrast) and resolution can be adjusted a posteriori during processing of the original time-domain data by iterative image reconstruction in a unique way not possible in conventional rf-pulse-dependent magnetic resonance imaging (MRI). The 3D SNI is demonstrated as a proof of concept on a commercial 700 MHz high-resolution NMR spectrometer, using a 3D-printed polymeric phantom immersed in water.

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Мартышкин, А. А., Е. Н. Бегинин, С. Е. Шешукова, Ю. П. Шараевский, С. А. Никитов, and А. В. Садовников. "Особенности формирования запрещенных зон при многомодовом распространении спиновых волн в магнонных кристаллах." Физика твердого тела 64, no. 9 (2022): 1278. http://dx.doi.org/10.21883/ftt.2022.09.52819.17hh.

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The dynamics of spin waves during their multimode propagation in a magnonic crystal, which is an irregular narrow ferrite waveguide with periodic boundary modulation, has been studied by the method of Mandelstam-Brillouin spectroscopy. The transformation of the mode composition of spin waves propagating in an irregular ferrite waveguide is shown. The space-time dynamics of spin waves and the characteristics of the band gaps of a magnonic crystal are experimentally studied, and the possibility of controlling the frequency-selective properties of such a structure is shown. By excitation of a superposition of even or odd width modes of the ferrite microstructure, it becomes possible to control the position of the band gaps of a magnonic crystal. The results of the experiment agree with the results of micromagnetic modeling of the propagation and transformation of the spectrum of spin waves propagating in a ferromagnetic periodic structure.

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47

Feng, Yongqiang, Taishan Wang, Jingyi Wu, Zhuxia Zhang, Li Jiang, Hongbin Han, and Chunru Wang. "Electron-spin excitation by implanting hydrogen into metallofullerene: the synthesis and spectroscopic characterization of Sc4C2H@Ih-C80." Chem. Commun. 50, no. 81 (2014): 12166–68. http://dx.doi.org/10.1039/c4cc05783j.

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48

Adhikary, Ganesh, Tanusree Saha, Primož Rebernik Ribič, Matija Stupar, Barbara Ressel, Jurij Urbančič, Giovanni De Ninno, A. Thamizhavel, and Kalobaran Maiti. "Orbital selective dynamics in Fe-pnictides triggered by polarized pump pulse excitations." Europhysics Letters 136, no. 1 (October 1, 2021): 17002. http://dx.doi.org/10.1209/0295-5075/ac2dc0.

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Abstract Quantum materials display exotic behaviours related to the interplay between temperature-driven phase transitions. Here, we study the electron dynamics in one such material, CaFe2As2, a parent Fe-based superconductor, employing time- and angle-resolved photoemission spectroscopy. CaFe2As2 exhibits concomitant transition to spin density wave state and tetragonal to orthorhombic structure below 170 K. The Fermi surface of this material consists of three hole pockets , β and around the Γ-point and two electron pockets around the X-point. The hole pockets have d xy , d yz and d zx orbital symmetries. The β band constituted by d xz /d yz orbitals exhibits a gap across the magnetic phase transition. We discover that polarized pump pulses can induce excitations of electrons of a selected symmetry. More specifically, while s-polarized light (polarization vector perpendicular to the xz plane) excites electrons corresponding to all the three hole bands, p-polarized light excites electrons essentially from , bands which are responsible for magnetic order. Interestingly, within the magnetically ordered phase, the excitation due to the p-polarized pump pulses occur at a time scale of 50 fs, which is significantly faster than the excitation induced by s-polarized light (∼200 fs). These results suggest that the relaxation of different ordered phases occurs at different time scales and this method can be used to achieve selective excitations to disentangle complexity in the study of quantum materials.

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Geoghegan, Mark, Marta M. Mróz, Chiara Botta, Laurie Parrenin, Cyril Brochon, Eric Cloutet, Eleni Pavlopoulou, Georges Hadziioannou, and Tersilla Virgili. "Optical Gain in Semiconducting Polymer Nano and Mesoparticles." Molecules 26, no. 4 (February 20, 2021): 1138. http://dx.doi.org/10.3390/molecules26041138.

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The presence of excited-states and charge-separated species was identified through UV and visible laser pump and visible/near-infrared probe femtosecond transient absorption spectroscopy in spin coated films of poly[N-9″-heptadecanyl-2,7-carbazole-alt-5,5-(4,7-di-2-thienyl-2′,1′,3′-benzothiadiazole)] (PCDTBT) nanoparticles and mesoparticles. Optical gain in the mesoparticle films is observed after excitation at both 400 and 610 nm. In the mesoparticle film, charge generation after UV excitation appears after around 50 ps, but little is observed after visible pump excitation. In the nanoparticle film, as for a uniform film of the pure polymer, charge formation was efficiently induced by UV excitation pump, while excitation of the low energetic absorption states (at 610 nm) induces in the nanoparticle film a large optical gain region reducing the charge formation efficiency. It is proposed that the different intermolecular interactions and molecular order within the nanoparticles and mesoparticles are responsible for their markedly different photophysical behavior. These results therefore demonstrate the possibility of a hitherto unexplored route to stimulated emission in a conjugated polymer that has relatively undemanding film preparation requirements.

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Weil, J. A., and D. F. Howarth. "Magnetic resonance spectroscopy of extra-terrestrial methyl radical." Canadian Journal of Physics 87, no. 6 (June 2009): 709–19. http://dx.doi.org/10.1139/p09-010.

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The particular molecule discussed in some detail herein is the methyl radical, CH3, with emphasis on its potential extraterrestrial appearance. In earlier papers, including group-theoretical analysis, it was shown that the isotropic EPR spectra of free radical (S = 1/2) species XLn, where the n equivalent nuclei also have spin 1/2, have a more complicated form than disclosed by the usual (first-order) oversimplified analysis. In the present work, we focus on the magnetic resonance of such systems at or near zero external magnetic field, and on the spectra obtained both by perpendicular [Formula: see text] and parallel-field [Formula: see text] excitation. This work summarizes what is known about the spin-flip transitions of CH3, and predicts what likely will be observed (0–200 MHz, under various field and scan conditions), for the future use by astrophysicists.

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Journal articles on the topic 'Spectroscopie à excitation de spin'

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