Fermi Liquid Theory of d -Wave Altermagnets: Demon Modes and Fano-Demon States
Year: 2025
Type: article
Abstract: We develop a Fermi liquid theory of d-wave altermagnets and apply it to describe their collective excitation spectrum. We predict that in addition to a conventional undamped plasmon mode, where both spin components oscillate in phase, there is an acoustic plasmon (or demon) mode with out-of-phase spin dynamics. By analyzing the dynamical structure factor, we reveal a strong dependence of the demon's frequency and spectral weight both on the Landau parameters and on the direction of propagation. Notably, as a function of the propagation angle, we show that the acoustic mode evolves from a hidden state, which has zero spectral weight in the density excitation spectrum, to a weakly damped propagating demon mode and then (below a critical interaction parameter) to a Fano-demon mixed state, which is marked by a strong hybridization with particle-hole excitations and a corresponding asymmetric line shape in the structure factor. Our Letter paves the way for applications of altermagnetic materials in optospintronics by harnessing collective electron spin oscillations beyond traditional magnon spin waves.
Source: Physical Review Letters
DOI: 10.1103/zqz6-sq2n
Authors: Habib Rostami, Johannes Hofmann
Language: English
Subfield: Condensed Matter Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $3,750
OpenAlex ID: W4417016787