Jure Demsar

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The organizations/institutes from the scholar's latest article

Johannes Gutenberg University Mainz

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Jure Demsar has a total of 545 co-authors. Here are the top co-authors by number of shared publications:

Dragan Mihailovic
Jožef Stefan Institute, Ljubljana, Slovenia
19 shared publications
V. V. Kabanov
Jozef Stefan Institute,1000 Ljubljana, Slovenia
13 shared publications
Hans-Joachim Elmers
Johannes Gutenberg-Universität Mainz
12 shared publications
Dmytro Kutnyakhov
Deutsches Elektronen-Synchrotron DESY
9 shared publications
Steinn Ymir Agustsson
Johannes Gutenberg-Universität, Institute of Physics, Mainz, Germany
8 shared publications
A. J. Taylor
Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
7 shared publications

Latest Publications

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Open Access
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- 12 June 2026
- Published by Wiley in Advanced Science
Strain Tuning the Occupation of Candidate Topological Weyl States in W‐Doped MoTe ₂
by Amon Lanz, Olena Tkach, Yaryna Lytvynenko, Florian Diekmann, Harshit Agarwal, Sofia Michaela Souliou, Mehdi Frachet, Michael Merz, Sergii V. Chernov, Andrei Gloskovskii, et al.
Strain‐induced modifications of the electronic structure in ‐ were studied using hard X‐ray angle‐resolved photoemission spectroscopy (HARPES). Partial substitution of Mo with W stabilizes the metastable low‐temperature orthorhombic phase of . Samples were first characterized by angle‐resolved photoemission spectroscopy experiments with soft X‐rays and higher resolution, showing good agreement with ab initio calculations of electronic states related to topology. The modification of the bulk electronic structure due to the applied strain was assessed using operando HARPES. Applying tensile strain along the ‐axis with amplitudes up to 0.34% result in changes in the bulk electronic structure as predicted by previous ab‐initio calculations. In particular, the results demonstrate a strain‐driven depletion of electronic states with heavy masses and high scattering rates, leading to an increase in conductivity. In contrast, tensile strain along the ‐axis results in a significant increase in resistivity, which we confirmed by transport studies.
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- 12 June 2026
- Published by Wiley in Advanced Science
Open Access
Strain Tuning the Occupation of Candidate Topological Weyl States in W‐Doped MoTe ₂
by Amon Lanz, Olena Tkach, Yaryna Lytvynenko, Florian Diekmann, Harshit Agarwal, Sofia Michaela Souliou, Mehdi Frachet, Michael Merz, Sergii V. Chernov, Andrei Gloskovskii, et al.
Strain‐induced modifications of the electronic structure in ‐ were studied using hard X‐ray angle‐resolved photoemission spectroscopy (HARPES). Partial substitution of Mo with W stabilizes the metastable low‐temperature orthorhombic phase of . Samples were first characterized by angle‐resolved photoemission spectroscopy experiments with soft X‐rays and higher resolution, showing good agreement with ab initio calculations of electronic states related to topology. The modification of the bulk electronic structure due to the applied strain was assessed using operando HARPES. Applying tensile strain along the ‐axis with amplitudes up to 0.34% result in changes in the bulk electronic structure as predicted by previous ab‐initio calculations. In particular, the results demonstrate a strain‐driven depletion of electronic states with heavy masses and high scattering rates, leading to an increase in conductivity. In contrast, tensile strain along the ‐axis results in a significant increase in resistivity, which we confirmed by transport studies.
Open Access
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- 1 June 2026
- Published by Springer Nature in Research Square
Direct Observation of Chiral Magnon Splitting in Altermagnetic CrSb
by Hans-Joachim Elmers, Yaryna Lytvynenko, Chafic Fawaz, Tom Lacmann, Sergii Chernov, Olena Tkach, Harshit Agarwal, Jan Schunck, Dmytro Kutnyakhov, Jakob Dilling, et al.
Altermagnetism, a novel class of magnetic order, has recently attracted the scientific interest. Combining the favourable properties of ferromagnets, such as spin polarised conduction electrons, with the advantages of antiferromagnets, such as zero net magnetisation and high-frequency switching, it is a promising area of research. While the ground state properties of altermagnets have been studied, their dynamic properties, such as magnon dispersions, remain elusive. Understanding these properties includes the investigation of magnon excitations, which is essential for the development of spintronic and magnonic devices based on altermagnets. In this study, we measure the energy splitting of altermagnetic magnons with opposite chirality in the hexagonal altermagnet CrSb using a unique combination of angle-resolved photoemission spectroscopy and resonant inelastic X-ray scattering. We selectively excite electronic and magnonic states with opposite spins and quantify their energy splitting. We find that the non-degeneracy of electronic and magnonic states exists away from high-symmetry directions in good agreement with recent ab initio calculations. Our experimental proof of chiral magnons demonstrates a new degree of freedom in magnetism that is both of fundamental importance and opens the door to the exploration of the non-reciprocal transport properties of these bosons in devices.
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- 1 June 2026
- Published by Springer Nature in Research Square
Open Access
Direct Observation of Chiral Magnon Splitting in Altermagnetic CrSb
by Hans-Joachim Elmers, Yaryna Lytvynenko, Chafic Fawaz, Tom Lacmann, Sergii Chernov, Olena Tkach, Harshit Agarwal, Jan Schunck, Dmytro Kutnyakhov, Jakob Dilling, et al.
Altermagnetism, a novel class of magnetic order, has recently attracted the scientific interest. Combining the favourable properties of ferromagnets, such as spin polarised conduction electrons, with the advantages of antiferromagnets, such as zero net magnetisation and high-frequency switching, it is a promising area of research. While the ground state properties of altermagnets have been studied, their dynamic properties, such as magnon dispersions, remain elusive. Understanding these properties includes the investigation of magnon excitations, which is essential for the development of spintronic and magnonic devices based on altermagnets. In this study, we measure the energy splitting of altermagnetic magnons with opposite chirality in the hexagonal altermagnet CrSb using a unique combination of angle-resolved photoemission spectroscopy and resonant inelastic X-ray scattering. We selectively excite electronic and magnonic states with opposite spins and quantify their energy splitting. We find that the non-degeneracy of electronic and magnonic states exists away from high-symmetry directions in good agreement with recent ab initio calculations. Our experimental proof of chiral magnons demonstrates a new degree of freedom in magnetism that is both of fundamental importance and opens the door to the exploration of the non-reciprocal transport properties of these bosons in devices.
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Cited by 1
- 3 December 2025
- Published by American Physical Society (APS) in Physical Review B
Orbital magnetization in the Nb-substituted kagome metal CsV 3 Sb 5
by H. J. Elmers, O. Tkach, Y. Lytvynenko, H. Agarwal, D. Biswas, J. Liu, A.-A. Haghighirad, M. Merz, S. Pakhira, G. Garbarino, et al.
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- 3 December 2025
- Published by American Physical Society (APS) in Physical Review B
Orbital magnetization in the Nb-substituted kagome metal CsV 3 Sb 5
by H. J. Elmers, O. Tkach, Y. Lytvynenko, H. Agarwal, D. Biswas, J. Liu, A.-A. Haghighirad, M. Merz, S. Pakhira, G. Garbarino, et al.
Cited by 1
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Cited by 27
- 6 March 2025
- Published by American Physical Society (APS) in Physical Review Letters
Chirality in the Kagome Metal ${CsV}_{3} {Sb}_{5}$
by H. J. Elmers, O. Tkach, Y. Lytvynenko, P. Yogi, M. Schmitt, D. Biswas, J. Liu, S. V. Chernov, Quynh Nguyen, M. Hoesch, et al.
Using x-ray photoelectron diffraction (XPD) and angle-resolved photoemission spectroscopy, we study photoemission intensity changes related to changes in the geometric and electronic structure in the kagome metal CsV_{3}Sb_{5} upon transition to an unconventional charge density wave (CDW) state. The XPD patterns reveal the presence of a chiral atomic structure in the CDW phase. Furthermore, using circularly polarized x-rays, we have found a pronounced nontrivial circular dichroism in the angular distribution of the valence band photoemission in the CDW phase, indicating a chirality of the electronic structure. This observation is consistent with the proposed orbital loop current order. In view of a negligible spontaneous Kerr signal in recent magneto-optical studies, the results suggest an antiferromagnetic coupling of the orbital magnetic moments along the c axis. While the inherent structural chirality may also induce circular dichroism, the observed asymmetry values seem to be too large in the case of the weak structural distortions caused by the CDW.
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- 6 March 2025
- Published by American Physical Society (APS) in Physical Review Letters
Chirality in the Kagome Metal ${CsV}_{3} {Sb}_{5}$
by H. J. Elmers, O. Tkach, Y. Lytvynenko, P. Yogi, M. Schmitt, D. Biswas, J. Liu, S. V. Chernov, Quynh Nguyen, M. Hoesch, et al.
Using x-ray photoelectron diffraction (XPD) and angle-resolved photoemission spectroscopy, we study photoemission intensity changes related to changes in the geometric and electronic structure in the kagome metal CsV_{3}Sb_{5} upon transition to an unconventional charge density wave (CDW) state. The XPD patterns reveal the presence of a chiral atomic structure in the CDW phase. Furthermore, using circularly polarized x-rays, we have found a pronounced nontrivial circular dichroism in the angular distribution of the valence band photoemission in the CDW phase, indicating a chirality of the electronic structure. This observation is consistent with the proposed orbital loop current order. In view of a negligible spontaneous Kerr signal in recent magneto-optical studies, the results suggest an antiferromagnetic coupling of the orbital magnetic moments along the c axis. While the inherent structural chirality may also induce circular dichroism, the observed asymmetry values seem to be too large in the case of the weak structural distortions caused by the CDW.
Cited by 27
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Cited by 4
- 1 November 2023
- Published by American Physical Society (APS) in Physical Review Letters
Possible Eliashberg-Type Superconductivity Enhancement Effects in a Two-Band Superconductor ${MgB}_{2}$ Driven by Narrow-Band THz Pulses
by Sergei Sobolev, Amon P. Lanz, Tao Dong, Amrit Pokharel, Viktor Kabanov, Tie-Quan Xu, Yue Wang, Zi-Zhao Gan, Li-Yu Shi, Nan-Lin Wang, et al.
We study THz-driven condensate dynamics in epitaxial thin films of ${MgB}_{2}$ , a prototype two-band superconductor (SC) with weak interband coupling. The temperature and excitation density dependent dynamics follow the behavior predicted by the phenomenological bottleneck model for the single-gap SC, implying adiabatic coupling between the two condensates on the ps timescale. The amplitude of the THz-driven suppression of condensate density reveals an unexpected decrease in pair-breaking efficiency with increasing temperature—unlike in the case of optical excitation. The reduced pair-breaking efficiency of narrow-band THz pulses, displaying minimum near $\approx 0.7 T_{c}$ , is attributed to THz-driven, long-lived, nonthermal quasiparticle distribution, resulting in Eliashberg-type enhancement of superconductivity, competing with pair breaking.
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- 1 November 2023
- Published by American Physical Society (APS) in Physical Review Letters
Possible Eliashberg-Type Superconductivity Enhancement Effects in a Two-Band Superconductor ${MgB}_{2}$ Driven by Narrow-Band THz Pulses
by Sergei Sobolev, Amon P. Lanz, Tao Dong, Amrit Pokharel, Viktor Kabanov, Tie-Quan Xu, Yue Wang, Zi-Zhao Gan, Li-Yu Shi, Nan-Lin Wang, et al.
We study THz-driven condensate dynamics in epitaxial thin films of ${MgB}_{2}$ , a prototype two-band superconductor (SC) with weak interband coupling. The temperature and excitation density dependent dynamics follow the behavior predicted by the phenomenological bottleneck model for the single-gap SC, implying adiabatic coupling between the two condensates on the ps timescale. The amplitude of the THz-driven suppression of condensate density reveals an unexpected decrease in pair-breaking efficiency with increasing temperature—unlike in the case of optical excitation. The reduced pair-breaking efficiency of narrow-band THz pulses, displaying minimum near $\approx 0.7 T_{c}$ , is attributed to THz-driven, long-lived, nonthermal quasiparticle distribution, resulting in Eliashberg-type enhancement of superconductivity, competing with pair breaking.
Cited by 4
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Cited by 2
- 25 September 2023
- Published by American Physical Society (APS) in Physical Review B
Electron-phonon coupling at the Te $5 p$ hole pocket in ${TiTe}_{2}$
by O. Fedchenko, D. Vasilyev, D. Kutnyakhov, S. Babenkov, S. Chernov, T. Grunske, T. Kauerhof, K. von Volkmann, J. Demsar, K. Rossnagel, et al.
We have determined the quasiparticle dispersion for semimetallic $1 T − {TiTe}_{2}$ at 20 K using time-of-flight momentum microscopy with tunable soft-x-ray excitation and high-resolution momentum microscopy with 6.4 eV ultraviolet excitation. In particular, we have studied the quasiparticle interactions of the electronic states of the Te $5 p$ –hole pockets with high Fermi velocity near the $Γ$ point. Kinks in the otherwise parabolic dispersions suggest the onset of many-body interactions at a binding energy of about 30 meV. We attribute these kinks to electron-phonon coupling. Our study complements previously published results on the Ti $3 d$ electron pockets near the $M$ and $L$ points. The electron-phonon coupling parameters ( $λ = 0.3$ –0.8) are in agreement with previously reported values. An apparently nonzero real part of the self-energy at the Fermi level for one of the two bands may be caused by residual charge-density-wave fluctuations.
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- 25 September 2023
- Published by American Physical Society (APS) in Physical Review B
Electron-phonon coupling at the Te $5 p$ hole pocket in ${TiTe}_{2}$
by O. Fedchenko, D. Vasilyev, D. Kutnyakhov, S. Babenkov, S. Chernov, T. Grunske, T. Kauerhof, K. von Volkmann, J. Demsar, K. Rossnagel, et al.
We have determined the quasiparticle dispersion for semimetallic $1 T − {TiTe}_{2}$ at 20 K using time-of-flight momentum microscopy with tunable soft-x-ray excitation and high-resolution momentum microscopy with 6.4 eV ultraviolet excitation. In particular, we have studied the quasiparticle interactions of the electronic states of the Te $5 p$ –hole pockets with high Fermi velocity near the $Γ$ point. Kinks in the otherwise parabolic dispersions suggest the onset of many-body interactions at a binding energy of about 30 meV. We attribute these kinks to electron-phonon coupling. Our study complements previously published results on the Ti $3 d$ electron pockets near the $M$ and $L$ points. The electron-phonon coupling parameters ( $λ = 0.3$ –0.8) are in agreement with previously reported values. An apparently nonzero real part of the self-energy at the Fermi level for one of the two bands may be caused by residual charge-density-wave fluctuations.
Cited by 2
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Cited by 3
- 15 September 2023
- Published by American Physical Society (APS) in Physical Review B
Control of the asymmetric band structure in ${Mn}_{2} Au$ by a ferromagnetic driver layer
by Y. Lytvynenko, O. Fedchenko, S. V. Chernov, S. Babenkov, D. Vasilyev, O. Tkach, A. Gloskovskii, T. R. F. Peixoto, C. Schlueter, V. Grigorev, et al.
Hard x-ray angle-resolved photoemission spectroscopy reveals the momentum-resolved band structure in an epitaxial ${Mn}_{2} Au$ (001) film capped by a 2-nm-thick ferromagnetic permalloy layer. By magnetizing the permalloy capping layer, the exceptionally strong exchange bias aligns the Néel vector in the ${Mn}_{2} Au$ (001) film accordingly. Uncompensated interface Mn magnetic moments in ${Mn}_{2} Au$ were identified as the origin of the exchange bias using x-ray magnetic circular dichroism in combination with photoelectron emission microscopy. Using time-of-flight momentum microscopy, we measure the asymmetry of the band structure, $E (k) \neq E (- k)$ , in ${Mn}_{2} Au$ resulting from the homogeneous orientation of the Néel vector. Comparison with theory shows that the Néel vector, determined by the magnetic moment of the top Mn layer, is antiparallel to the permalloy magnetization. The experimental results demonstrate that hard x-ray photoemission spectroscopy can measure the band structure of epitaxial layers beneath a metallic capping layer and corroborate the asymmetric band structure in ${Mn}_{2} Au$ that was previously inferred only indirectly.
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- 15 September 2023
- Published by American Physical Society (APS) in Physical Review B
Control of the asymmetric band structure in ${Mn}_{2} Au$ by a ferromagnetic driver layer
by Y. Lytvynenko, O. Fedchenko, S. V. Chernov, S. Babenkov, D. Vasilyev, O. Tkach, A. Gloskovskii, T. R. F. Peixoto, C. Schlueter, V. Grigorev, et al.
Hard x-ray angle-resolved photoemission spectroscopy reveals the momentum-resolved band structure in an epitaxial ${Mn}_{2} Au$ (001) film capped by a 2-nm-thick ferromagnetic permalloy layer. By magnetizing the permalloy capping layer, the exceptionally strong exchange bias aligns the Néel vector in the ${Mn}_{2} Au$ (001) film accordingly. Uncompensated interface Mn magnetic moments in ${Mn}_{2} Au$ were identified as the origin of the exchange bias using x-ray magnetic circular dichroism in combination with photoelectron emission microscopy. Using time-of-flight momentum microscopy, we measure the asymmetry of the band structure, $E (k) \neq E (- k)$ , in ${Mn}_{2} Au$ resulting from the homogeneous orientation of the Néel vector. Comparison with theory shows that the Néel vector, determined by the magnetic moment of the top Mn layer, is antiparallel to the permalloy magnetization. The experimental results demonstrate that hard x-ray photoemission spectroscopy can measure the band structure of epitaxial layers beneath a metallic capping layer and corroborate the asymmetric band structure in ${Mn}_{2} Au$ that was previously inferred only indirectly.
Cited by 3
Open Access
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Cited by 11
- 28 July 2023
- Published by American Physical Society (APS) in Physical Review B
Combined investigation of collective amplitude and phase modes in a quasi-one-dimensional charge density wave system over a wide spectral range
by Konstantin Warawa, Nicolas Christophel, Sergei Sobolev, Jure Demsar, Hartmut G. Roskos, Mark D. Thomson
We investigate experimentally both the amplitude and phase channels of the collective modes in the quasi-1D charge-density-wave (CDW) system, $K_{0.3} {MoO}_{3}$ , by combining (i) optical impulsive-Raman pump-probe and (ii) terahertz (THz) time-domain spectroscopy, with high resolution and a detailed analysis of the full complex-valued spectra in both cases. This allows an unequivocal assignment of the observed bands to CDW modes across the THz range up to $9 THz$ . We revise and extend a time-dependent Ginzburg-Landau model to account for the observed temperature dependence of the modes, where the combination of both amplitude and phase modes allows one to robustly determine the bare-phonon frequencies and electron-phonon (e-ph) coupling parameters. While the e-ph coupling is indeed strongest for the lowest-energy phonon, dropping sharply for the next higher frequency phonons, it grows back significantly for the higher-energy phonons, demonstrating their important role in driving the CDW formation. We also include a reassessment of our previous analysis of the lowest-lying phase modes. Assuming weaker electronic damping for the phase channel results in a qualitative picture more consistent with quantum-mechanical treatments of the collective modes, with a strongly coupled amplitudon and phason being the lowest frequency modes.
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- 28 July 2023
- Published by American Physical Society (APS) in Physical Review B
Open Access
Combined investigation of collective amplitude and phase modes in a quasi-one-dimensional charge density wave system over a wide spectral range
by Konstantin Warawa, Nicolas Christophel, Sergei Sobolev, Jure Demsar, Hartmut G. Roskos, Mark D. Thomson
We investigate experimentally both the amplitude and phase channels of the collective modes in the quasi-1D charge-density-wave (CDW) system, $K_{0.3} {MoO}_{3}$ , by combining (i) optical impulsive-Raman pump-probe and (ii) terahertz (THz) time-domain spectroscopy, with high resolution and a detailed analysis of the full complex-valued spectra in both cases. This allows an unequivocal assignment of the observed bands to CDW modes across the THz range up to $9 THz$ . We revise and extend a time-dependent Ginzburg-Landau model to account for the observed temperature dependence of the modes, where the combination of both amplitude and phase modes allows one to robustly determine the bare-phonon frequencies and electron-phonon (e-ph) coupling parameters. While the e-ph coupling is indeed strongest for the lowest-energy phonon, dropping sharply for the next higher frequency phonons, it grows back significantly for the higher-energy phonons, demonstrating their important role in driving the CDW formation. We also include a reassessment of our previous analysis of the lowest-lying phase modes. Assuming weaker electronic damping for the phase channel results in a qualitative picture more consistent with quantum-mechanical treatments of the collective modes, with a strongly coupled amplitudon and phason being the lowest frequency modes.
Cited by 11
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Cited by 6
- 28 July 2023
- Published by American Physical Society (APS) in Physical Review B
Collective modes in the charge density wave state of $K_{0.3} {MoO}_{3}$ : Role of long-range Coulomb interactions revisited
by Max O. Hansen, Yash Palan, Viktor Hahn, Mark D. Thomson, Konstantin Warawa, Hartmut G. Roskos, Jure Demsar, Falko Pientka, Oleksandr Tsyplyatyev, Peter Kopietz
We re-examine the effect of long-range Coulomb interactions on the collective amplitude and phase modes in the incommensurate charge-density-wave ground state of quasi-one-dimensional conductors.Using an effective action approach we show that the longitudinal acoustic phonon protects the gapless linear dispersion of the lowest phase mode in the presence of long-range Coulomb interactions. Moreover, in Gaussian approximation, amplitude fluctuations are not affected by long-range Coulomb interactions. We also calculate the collective mode dispersions at finite temperatures and compare our results with the measured energies of amplitude and phase modes in $K_{0.3} {MoO}_{3}$ . With the exception of the lowest phase mode, the temperature dependence of the measured mode energies can be quantitatively described within a multiphonon Fröhlich model for generic electron-phonon interactions neglecting long-range Coulomb interactions.
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- 28 July 2023
- Published by American Physical Society (APS) in Physical Review B
Collective modes in the charge density wave state of $K_{0.3} {MoO}_{3}$ : Role of long-range Coulomb interactions revisited
by Max O. Hansen, Yash Palan, Viktor Hahn, Mark D. Thomson, Konstantin Warawa, Hartmut G. Roskos, Jure Demsar, Falko Pientka, Oleksandr Tsyplyatyev, Peter Kopietz
We re-examine the effect of long-range Coulomb interactions on the collective amplitude and phase modes in the incommensurate charge-density-wave ground state of quasi-one-dimensional conductors.Using an effective action approach we show that the longitudinal acoustic phonon protects the gapless linear dispersion of the lowest phase mode in the presence of long-range Coulomb interactions. Moreover, in Gaussian approximation, amplitude fluctuations are not affected by long-range Coulomb interactions. We also calculate the collective mode dispersions at finite temperatures and compare our results with the measured energies of amplitude and phase modes in $K_{0.3} {MoO}_{3}$ . With the exception of the lowest phase mode, the temperature dependence of the measured mode energies can be quantitatively described within a multiphonon Fröhlich model for generic electron-phonon interactions neglecting long-range Coulomb interactions.
Cited by 6
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Cited by 5
- 4 May 2023
- Published by American Physical Society (APS) in Physical Review B
Selective coupling of coherent optical phonons in ${YBa}_{2} {Cu}_{3} O_{7 - δ}$ with electronic transitions
by Kunie Ishioka, Alexej Pashkin, Christian Bernhard, Hrvoje Petek, Xin Yao, Jure Demsar
We investigate coherent lattice dynamics in optimally doped ${YBa}_{2} {Cu}_{3} O_{7 - δ}$ driven by ultrashort ( $\sim 12$ fs) near-infrared and near-ultraviolet pulses. Transient reflectivity experiments, performed at room temperature and under moderate ( $< 0.1$ mJ/ ${cm}^{2}$ ) excitation fluence, reveal $A_{g}$ -symmetry phonon modes related to the O(2,3) bending in the ${CuO}_{2}$ planes and to the apical O(4) stretching at frequencies between 10 and 15 THz, in addition to the previously reported Ba and Cu(2) vibrations at 3.5 and 4.5 THz. The relative coherent phonon amplitudes are in stark contrast to the relative phonon intensities in the spontaneous Raman scattering spectrum excited at the same wavelength. This contrast indicates mode-dependent contributions of the Raman and non-Raman mechanisms to the coherent phonon generation. We show that the particularly intense coherent Cu(2) phonon, together with its initial phase, supports its generation predominately via a displacive mechanism, possibly involving the charge transfer within the ${CuO}_{2}$ planes. The small amplitude of the coherent out-of-phase O(2,3) bending mode at 10 THz also suggests the involvement of non-Raman generation mechanism. The generation of the other coherent phonons can in principle be explained within the framework of Raman mechanism. When the pump light has the polarization component perpendicular to the ${CuO}_{2}$ plane, the coherent O(4) mode at 15 THz is strongly enhanced compared to the in-plane excitation, corresponding to the large polarizability component associated with the hopping between the apical and the chain oxygens, O(4) and O(1).
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- 4 May 2023
- Published by American Physical Society (APS) in Physical Review B
Selective coupling of coherent optical phonons in ${YBa}_{2} {Cu}_{3} O_{7 - δ}$ with electronic transitions
by Kunie Ishioka, Alexej Pashkin, Christian Bernhard, Hrvoje Petek, Xin Yao, Jure Demsar
We investigate coherent lattice dynamics in optimally doped ${YBa}_{2} {Cu}_{3} O_{7 - δ}$ driven by ultrashort ( $\sim 12$ fs) near-infrared and near-ultraviolet pulses. Transient reflectivity experiments, performed at room temperature and under moderate ( $< 0.1$ mJ/ ${cm}^{2}$ ) excitation fluence, reveal $A_{g}$ -symmetry phonon modes related to the O(2,3) bending in the ${CuO}_{2}$ planes and to the apical O(4) stretching at frequencies between 10 and 15 THz, in addition to the previously reported Ba and Cu(2) vibrations at 3.5 and 4.5 THz. The relative coherent phonon amplitudes are in stark contrast to the relative phonon intensities in the spontaneous Raman scattering spectrum excited at the same wavelength. This contrast indicates mode-dependent contributions of the Raman and non-Raman mechanisms to the coherent phonon generation. We show that the particularly intense coherent Cu(2) phonon, together with its initial phase, supports its generation predominately via a displacive mechanism, possibly involving the charge transfer within the ${CuO}_{2}$ planes. The small amplitude of the coherent out-of-phase O(2,3) bending mode at 10 THz also suggests the involvement of non-Raman generation mechanism. The generation of the other coherent phonons can in principle be explained within the framework of Raman mechanism. When the pump light has the polarization component perpendicular to the ${CuO}_{2}$ plane, the coherent O(4) mode at 15 THz is strongly enhanced compared to the in-plane excitation, corresponding to the large polarizability component associated with the hopping between the apical and the chain oxygens, O(4) and O(1).
Cited by 5

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