Speaker
Description
Quantum materials exhibit a complex interplay between electronic correlations, topology, and magnetism, placing them at the forefront of condensed matter physics and quantum technology. Understanding these systems requires disentangling spin-orbit coupling, electron-electron interactions, and magnetic fluctuations under realistic conditions, including finite temperatures and structural disorder. Spin- and time-resolved angle-resolved photoemission spectroscopy (STARPES) is a crucial technique for probing electronic and spin structures in magnetic and topological materials. However, quantitative interpretation of spin-ARPES data necessitates advanced theoretical models that accurately capture electronic states, spin textures, and dynamic responses to external fields.
I will present a theoretical framework based on the fully relativistic multiple-scattering Green function KKR method [1], effectively modeling spin-dependent photoemission. This approach includes correlation effects via dynamical mean-field theory (DMFT) [2] and describes spin fluctuations using the alloy analogy model [3]. I will also discuss advances in calculating light-induced electronic excitations [4], highlighting their relevance to spin-ARPES studies of topological and magnetic quantum materials.
A novel application is the one-step model of photoemission in studying altermagnets and kagome magnetic materials. Altermagnets, exhibiting unconventional time-reversal symmetry breaking without net magnetization, are explored in RuO$_2$ and MnTe [5,6]. Spin-ARPES combined with the one-step model provides insights into lifted Kramers spin degeneracy, revealing their potential for spintronics. In kagome magnetic materials, persistent flat band splitting and selective band renormalization are observed in FeSn thin films [7], highlighting unique correlation effects and topological phenomena. These developments offer a comprehensive framework for exploring magnetic phenomena and spin dynamics in complex quantum materials.
Acknowledgements
I would like to thank the Quantum Materials for Sustainable Technologies (QM4ST) project with Reg. No. CZ.02.01.01/00/22_008/0004572, cofunded by the ERDF as part of the MŠMT.
References
[1] H. Ebert et al., “Calculating condensed matter properties using the KKR-Green’s function method—recent developments and applications,” Reports on Progress in Physics, vol. 74, no. 9. IOP Publishing, p. 096501, 2011. https://doi.org/10.1088/0034-4885/74/9/096501
[2] J. Minár, “Correlation effects in transition metals and their alloys studied using the fully self-consistent KKR-based LSDA + DMFT scheme,” Journal of Physics: Condensed Matter, vol. 23, no. 25. IOP Publishing, p. 253201, Jun. 08, 2011. https://doi.org/10.1088/0953-8984/23/25/253201
[3] J. Minár et al., “One-step model of photoemission at finite temperatures: Spin fluctuations of Fe(001),” Physical Review B, vol. 102, no. 3. American Physical Society (APS), 2020. https://doi.org/10.1103/physrevb.102.035107
[4] J. Braun et al., “Correlation, temperature and disorder: Recent developments in the one-step description of angle-resolved photoemission,” Physics Reports, vol. 740. Elsevier BV, pp. 1–34, 2018. https://doi.org/10.1016/j.physrep.2018.02.007
[5] J. Krempaský et al., “Altermagnetic lifting of Kramers spin degeneracy,” Nature, vol. 626, no. 7999. Springer Science and Business Media LLC, pp. 517–522, 2024. https://doi.org/10.1038/s41586-023-06907-7
[6] O. Fedchenko et al., “Observation of time-reversal symmetry breaking in the band structure of altermagnetic RuO 2,” Science Advances, vol. 10, no. 5. American Association for the Advancement of Science (AAAS), 2024. https://doi.org/10.1126/sciadv.adj4883
[7] Z. Ren et al., “Persistent flat band splitting and strong selective band renormalization in a kagome magnet thin film,” Nature Communications, vol. 15, no. 1. Springer Science and Business Media LLC, 2024. https://doi.org/10.1038/s41467-024-53722-3
