Analysis of Spin Current Generation by Elastic Waves in $f$-wave Altermagnets

Abstract

We theoretically investigate the mechanism of spin current generation induced by elastic waves in nonrelativistic magnets referred to as altermagnets. By analyzing an $f$-wave altermagnet formed by a three-sublattice noncollinear antiferromagnetic structure breaking the spatial inversion symmetry on a two-dimensional triangular lattice within the linear response theory, we show that the nonrelativistic antisymmetric spin-split band structure can give rise to spin current generation when either longitudinal or transverse elastic wave is applied. We find that the momentum dependence of the antisymmetric spin splitting leads to a characteristic direction-dependent spin current response. We also compare the present nonrelativistic magnetic-order-driven mechanism with the relativistic one in a nonmagnetic Rashba system. These findings highlight the potential of invesion-symmetry-breaking altermagnets as a spin current generator driven by elasticity without relying on the relativistic spin-orbit coupling.

Figures (7)

• Figure 1: (Color online) (a) Three-sublattice noncollinear magnetic structures on the triangular lattice; three sublattices are denoted as A, B, and C. The arrows on each site represent the spin directions. $t$ stands for the nearest-neighbor hopping amplitude. (b) Schematic of the antisymmetric spin-split band structure in momentum space under the magnetic structures in (a); the momentum dependence is given by $k_y(k_y^2 - 3k_x^2)\sigma_z$.
• Figure 2: (Color online) (Left panel) Antisymmetric spin-split band structure along the high-symmetry lines in the Brillouin zone (BZ) under the three-sublattice noncollinear spin configuration. The color represents the expectation value of the momentum-resolved spin polarization along the $z$-axis. (Right panel) Corresponding density of states.
• Figure 3: (Color online) Chemical potential $\mu$ dependence of the spin current response by the application of a longitudinal elastic wave in the $f$-wave altermagnet, showing (a) intraband and (b) interband contributions. The left panel shows the propagation direction of the longitudinal wave.
• Figure 4: (Color online) Broadening factor $\delta$ dependence of the spin current response for (a) the intraband and (b) interband components at $\mu=1.5$.
• Figure 5: (Color online) Angular dependence of the spin current response induced by dynamical strain due to the application of a longitudinal wave in the $f$-wave altermagnet, shown for (a) the $x$ component and (b) the $y$ component.