Current-Induced Spin-Wave Doppler Shift in Antiferromagnets

We theoretically study the spin dynamics in antiferromagnets (AFs) under influence of an electric current. identify two different sources spin-transfer torques that stem from uniform (\(\boldsymbol{v}_{n}\)) and staggered (\(\boldsymbol{v}_{\ell }\)) electron densities. While former is well recognized, latter often overlooked. show both \(\boldsymbol{v}_{n}\) \(\boldsymbol{v}_{\ell }\) contribute equally to spin-wave Doppler shift. Microscopic calculations are presented for electrons on a two-dimensional square lattice with nearest-neighbor (t) next-nearest-neighbor (t′) hopping, which interpolate opposite transport regimes strongly-coupled AF (t′/t ≪ 1) weakly-coupled ferromagnets ≫ 1). In regime 1), have signs, sign shift depends band filling; dominant near gap (near bottom or top). As t′/t increased, undergoes change whereas does not. limit vanishing t, coincide torque reduces ferromagnets.