The magnon spectra of g-type altermagnet bulk CrSb

TL;DR

Problem: understanding dynamical magnetic excitations in altermagnets, specifically CrSb, where spin-split bands give rise to altermagnons. Approach: MBPT calculation of magnon spectra via the transverse magnetic susceptibility $\chi^{-+}$ with $W$ from cRPA, expanded in MLWFs, and a scaling $W \rightarrow \lambda W$ with $\lambda \approx 1.24$ to enforce near-Goldstone behavior. Key findings: altermagnons exhibit a spin-channel energy splitting up to $40$ meV along A--M, reach $275$ meV at the K point, have linear dispersion near $\Gamma$, and lifetimes differ by up to $20$ fs due to exchange-split bands. Significance: reveals strongly anisotropic altermagnon dynamics with potential spintronic applications and demonstrates a MBPT workflow for AMs.

Abstract

We present a calculation of the magnon spectra and chiral lifetimes of altermagnons in bulk CrSb using the many-body perturbation theory. The spin-split band structure is evident in the magnon spectra. Altermagnons attain an energy of 275 meV at the K point of the Brillouin zone. Due to large spin splitting at a specific ${\bf q}$ point along the A - M direction, lifetime differences of chiral altermagnons reach approximately 20 fs.

Figures (6)

• Figure 1: The nonrelativistic electronic band structure of bulk CrSb. We observe a remarkable energy difference between majority (red) and minority (blue) spin bands along the $\Gamma$ - L and A - M directions.
• Figure 2: The dispersion of altermagnons in bulk CrSb with spin polarizations $S_z=\pm 1$.
• Figure 3: The dispersion of altermagnons for d $\rightarrow$ u (top) and u $\rightarrow$ d (bottom) spin channels at positive and negative frequencies. To facilitate direct comparison, the energies at negative frequencies are mirrored onto the positive frequency axis.
• Figure 4: The altermagnon spectra along the $\Gamma$ - L direction.
• Figure 5: The altermagnon spectra along the A - M direction.