Light-induced odd-parity altermagnets on dimerized lattices

Abstract

Altermagnets are an emerging class of collinear magnets with momentum-dependent spin splitting and zero net magnetization. These materials can be broadly classified into two categories based on the behavior of spin splitting at time-reversal-related momenta: even-parity and odd-parity altermagnets. While even-parity altermagnets have been thoroughly investigated both theoretically and experimentally, the systems capable of hosting odd-parity altermagnetism remain largely unexplored. In this work, we demonstrate that circularly polarized light dynamically converts collinear PT-symmetric antiferromagnets on dimerized lattices into odd parity p-wave altermagnets. Because of the underlying Dirac band structure of the dimerized lattice, we find that the resulting p-wave altermagnets can realize Chern insulators (2D) and Weyl semimetals (3D) under appropriate drive conditions. Our findings demonstrate that collinear antiferromagnets on dimerized lattices provide ideal platforms to investigate the dynamical generation of odd-parity altermagnetism.

Figures (4)

• Figure 1: Schematic of a collinear antiferromagnet on a 2D dimerized lattice under CPL irradiation. Red and blue arrows on the lattice represent magnetic moments of opposite directions. Thick (black) solid lines denote the bonds of dimerization. (a) When dimerization occurs along the $x$ direction (type-I), the Fermi surfaces with opposite spins undergo opposite shifts along the $y$ direction in the presence of CPL. (b) When dimerization is oriented along the $y$ direction (type-II), they instead shift oppositely along the $x$ direction.
• Figure 2: (a) Energy bands of the static (black, spin-degenerate) and CPL-driven ($A_0 = 1.8$, red/blue for spin up/down) systems. (b) Fermi surface at Fermi energy $E_{F}=0.2$ (solid lines) and $E_{F}=0.7$ (dashed lines), corresponding to the light-induced spin-split bands in (a). (c) Band gap evolution: closure at the critical drive (dashed, $A_0 = 1.04$) and reopening for a stronger drive (solid, $A_0 = 1.8$). (d) Topological phase diagram in the $(M, A_0)$ plane. The phase boundary separating the two regions with $C=0$ and $C=2$ is determined by the gap-closing condition: $M=\tilde{F}$. The value $M = 0.2$ is used in (a-c). Shared parameters for all panels are $t_{0}=1$, $t_{1}=0.2$, $t_{2}=1.5$, $\eta=1$, and $\omega=9$.
• Figure 3: Energy spectrum for a sample of cylindrical geometry. (a) $y$-normal edges: Spin-degenerate spectrum of chiral edge states. States on the bottom (top) edge are shown as solid (dashed) lines. (b) $x$-normal edges: Spin-split spectrum of chiral edge states. States on the left (right) edge are shown as solid (dashed) lines. Parameters are $t_{0}=1$, $t_{1}=0.2$, $t_{2}=1.5$, $M=0.2$, $\eta=1$, $A_{0}=1.8$, and $\omega=9$.
• Figure 4: (a) Realization of the 3D system through AB stacking. (b) Fermi surfaces of the CPL-driven system at a Fermi energy $E_{F}=0.8$. The red and blue contours represent the spin-up and spin-down branches, respectively. Left panel: CPL incident along the $z$ direction. Right panel: CPL incident along the $y$ direction. (c) Energy spectrum in the $k_x = 0$ plane, showing two Weyl points of each spin. (d) Berry curvature vector field in the $k_{x}=0$ plane containing the Weyl points. Arrows show the in-plane components $(\Omega_{y},\Omega_{z})$. Red and blue dots mark the Weyl points, which act as Berry flux sources (arrows flowing out) and sinks (arrows flowing in), respectively. The value $M=1$ is used in (b), and $M=0.4$ is used in (c) and (d). Other shared parameters are $t_{0}=1$, $t_{1}=0.2$, $t_{2}=0.5$, $t_{3}=2$, $\eta=1$, $A_{0}=1.8$, and $\omega=9$.