Spin-dependent quasiparticle lifetimes in altermagnets

TL;DR

This paper studies how many-body interactions like magnons and phonons affect the lifetimes and spectral features of spin-split electrons in altermagnets, providing insights for experimental detection and understanding of quasiparticle dynamics.

Contribution

It offers the first detailed theoretical analysis of quasiparticle lifetimes in altermagnets considering multiple interactions and their temperature dependence.

Findings

Spin-splitting remains resolvable despite many-body effects.

Distinct spectral broadening for up and down spins near the Fermi surface due to magnon coupling.

Temperature increases lead to greater broadening of electronic states.

Abstract

We investigate many-body effects on the spin-split electron bands in altermagnets by computing the electron self-energy arising from interactions with magnons, phonons, and hybridized magnon-phonon modes. These interactions lead to band broadening, which can obscure the intrinsic spin-splitting in spectroscopic measurements. We consider a $d$-wave Lieb lattice altermagnet as a representative example. Our results reveal that the spin-splitting remains spectroscopically resolvable and provide theoretical estimates of lifetime effects relevant for experimental detection. For electron-magnon coupling, we find a distinct difference between spectral function broadening for up and down spins close to the Fermi surface, which is not present in the case of electron-phonon coupling. We relate it to the spin splitting of the magnon modes in altermagnets. The results, including magneto-elastic coupling, are very similar to the pure magnon case. This provides insights into quasiparticle dynamics in altermagnets and contributes to the broader understanding of many-body interactions in spin-split systems. By including the temperature dependence of the self-energies, we also quantify how thermal fluctuations influence the broadening of the electronic states.