Enhancement of optical bandwidth in altermagnets

Abstract

The realization of the unconventional d-wave magnetism in materials necessitates a k · p Rashba Hamiltonian added to the altermagnetic two-band Hamiltonian. This brings about a two spin-split bands system with spin-orbit coupling (SOC) gap minimum about the azimurthal direction ϕk = nπ/2 (where the spin-vectors are tangential to the (kx, ky) plane) and it is found to be maximum about the direction ϕk = (2n + 1)π/4 (where the z-component of the spin vectors is maximum). We show in this thesis that the alternating spin-momentum coupling in altermagnets initiates an enhancement in the optical bandwidth of the system, a phenomena similar to that provided by the Dresselhaus SOC in semiconductor with bulk inversion asymmetry. In manifestation with the observation listed above, the optical conductivity displays a van-Hove singularity at points about the directions ϕk = nπ/2 and ϕk = (2n + 1)π/4 showing extrema whenever the frequecy is such that Ω = 2(E+ − E−)kF (ϕk).