Nonlinear nonreciprocal transport in antiferromagnets free from spin-orbit coupling

Abstract

We theoretically propose a realization of a nonlinear nonreciprocal transport in antiferromagnets without relying on the relativistic spin-orbit coupling. Through the symmetry and microscopic model analyses, we show that a local spin scalar chirality to induce an asymmetric band modulation becomes a source of a Drude-type nonlinear transport, while an electric polarization induced by a collinear spin configuration in a triangle unit leads to a Berry-curvature-dipole-type nonlinear transport. We demonstrate that 120 • antiferromagnetic ordering on a triangular lattice and a breathing kagome lattice in an external magnetic field are typical examples. Our results open a new direction of designing and engineering functional materials with showing rich parity-violating transport phenomena by spontaneous magnetic phase transitions.

Ferroaxial moment induced by vortex spin texture

“…The irreducible representations of T z and M 0 are represented by A − 1u and A − 2u under the ∞/mm1 group, respectively. T z and M 0 correspond to the odd-parity magnetic multipoles [41,[63][64][65], which are the sources of the linear magnetoelectric effect [66][67][68][69][70][71][72][73][74][75], nonlinear (spin) current generation [76][77][78][79][80][81][82][83][84], and nonreciprocal magnon excitations [85][86][87][88][89][90][91]. Similarly, one expects that G 0 and Q z (T 0 and M z ) are related to the vortices of G (T ), as shown in Table I, although we here do not consider them, since we focus on the ferroaxial nature induced by the vortex spin textures in Fig.…”

“…A typical example is a spontaneous electric polarization induced by a noncollinear antiferromagnetic ordering with the vector spin chirality degree of freedom [20][21][22][23][24][25][26][27][28][29]; the ferroelectric (time-reversal-even polar) property appears below the critical temperature. Another example is found in a noncoplanar antiferromagnetic ordering, where nonlinear nonreciprocal transport is caused by the asymmetric band modulation under the spatial distribution of the local spin scalar chirality [29][30][31][32][33][34][35]. In this case, the antiferromagnetic state accompanies the nature of ferroic time-reversal-odd polar-tensor quantities, which is referred to as ferromagnetic toroidicity.…”

Stacking-dependent nonreciprocal transport in magnetic skyrmions

“…In the present study, I investigate nonlinear nonreciprocal conductive phenomena under magnetic orderings in centrosymmetric lattice systems in the absence of spin-orbit coupling. Recent theoretical studies have revealed that spin structures breaking both spatial inversion and time-reversal symmetries can cause asymmetric electronic band modulations [30,31,32], and nonreciprocal transport [33,34,35] without the spin-orbit coupling. I further aim at exploring such nonlinear transport phenomena by targeting a magnetic skyrmion crystal (SkX), which is characterized by a periodic array of swirling noncoplanar spin textures [36,37,38,39,40,41,42].…”

Cluster Toroidal Multipoles Formed by Electric-Quadrupole and Magnetic-Octupole Trimers: A Possible Scenario for Hidden Orders in Ca$_5$Ir$_3$O$_{12}$

“…[1][2][3][4][5][6][7] There are two types of toroidal multipoles: magnetic toroidal (MT) multipoles with the same symmetry property as time-reversal-odd polar tensors and electric toroidal (ET) multipoles with the same symmetry as time-reversal-even axial tensors. Among them, the odd-parity toroidal multipoles, i.e., the odd-rank MT and even-rank ET multipoles, have been extensively studied, since they give rise to physical phenomena related to the spatial-parity breaking, such as the magnetoelectric effect under the MT dipole, [8][9][10][11][12][13][14][15][16][17] nonlinear (spin) transport [18][19][20][21][22][23][24][25] and nonreciprocal magnon excitations under the MT dipole and octupole, [26][27][28][29][30][31] and Edelstein effect and rotation-field induced electric polarization under the ET monopole and quadrupole. [32][33][34][35][36][37] These unconventional electronic orderings have been proposed and identified in metallic materials, such as the MT dipole orderings in UNi 4 B, 12,[38][39][40][41]…”