Speaker
Description
Altermagnets attract ongoing interest because of their unexpected electronic properties, such as spin splitting of electron bands or various transport properties (anomalous and spin Hall effects). Besides the electronic properties, based on elementary excitations that can be classified using the electron spin as a good quantum number, attention has recently been paid to magnons, where such simple classification is not possible. Nevertheless, magnon-related properties of altermagnets are interesting as well, including the chirality-based splitting of magnon eigenvalues [1] or various transport phenomena induced by temperature gradients [2, 3]. However, systematic classification of these magnon-related properties based on the group theory is not available at present.
In this contribution, magnons in a simple model of altermagnetism, corresponding to a two-dimensional bilayer, are studied within the classical isotropic Heisenberg Hamiltonian. Particular attention is paid to the splitting of magnon eigenvalues as well as to the spin currents generated by temperature gradients. The techniques used include the Bogoliubov transformation, the adiabatic linear-response theory, and the Shubnikov magnetic groups [4]. The obtained results are compared with those related to electronic excitations, namely, with the spin splitting of electron eigenvalues and with the spin currents generated by external electric fields. It is found that the previously developed classification scheme [4] is relevant for both electron-based and magnon-based properties.
Acknowledgements
The work was supported financially by the Czech Science Foundation (grant No. 23-04746S).
References
[1] L. Smejkal, et al., "Chiral magnons in altermagnetic RuO2," Physical Review Letters, vol. 131, no. 25. American Physical Society (APS), Dec. 20, 2023. https://doi.org/10.1103/physrevlett.131.256703
[2] M. Weißenhofer and A. Marmodoro, “Atomistic spin dynamics simulations of magnonic spin Seebeck and spin Nernst effects in altermagnets,” Physical Review B, vol. 110, no. 9. American Physical Society (APS), Sep. 19, 2024. https://doi.org/10.1103/physrevb.110.094427
[3] R. Hoyer et al., “Spontaneous crystal thermal Hall effect in insulating altermagnets,” Physical Review B, vol. 111, no. 2. American Physical Society (APS), Jan. 28, 2025. https://doi.org/10.1103/physrevb.111.l020412
[4] I. Turek, “Altermagnetism and magnetic groups with pseudoscalar electron spin,” Physical Review B, vol. 106, no. 9. American Physical Society (APS), Sep. 27, 2022. https://doi.org/10.1103/physrevb.106.094432
