Stability of Skyrmion Crystal Phase in Centrosymmetric Distorted Triangular-Lattice Antiferromagnets

Abstract

The stability of a magnetic skyrmion crystal in a centrosymmetric orthorhombic lattice system is numerically investigated. By performing the simulated annealing for an effective spin model with the momentumresolved interaction on a uniaxially distorted triangular lattice, we find that the skyrmion crystal is robustly realized when dominant interaction channels consist of the double-Q structure in momentum space. Moreover, we show that an anti-type skyrmion crystal with the opposite skyrmion number is obtained by tuning the sign of the bond-dependent anisotropic exchange interaction that originates from the relativistic spinorbit coupling.

Orthorhombic distortion and rectangular skyrmion crystal in a centrosymmetric tetragonal host

“…The formation of the R-SkX with the triple-Q modulation is reasonable, since the contribution to the free energy in the coupling form of (S 0 • S Q 1 )(S −Q 3 • S Q 4 ) occurs like the triangular SkX in hexagonal systems owing to the relation of the triple-Q ordering vectors as Q 1 + (−Q 3 ) + Q 4 = 0. Indeed, it was shown that a similar R-SkX remains stable on a uniaxially-distorted triangular lattice [47]. The above tendency holds for J Q 2 /J Q 1 > 1.…”

“…In these situations, the SkX is invariant under threefold or fourfold rotation. Meanwhile, it was revealed that SkXs remain stable in the low-symmetric lattice structures [42][43][44][45][46][47] and nonsymmorphic lattice structures with the screw axis [48]. In addition, a recent experiment has shown that a rhombic SkX was observed in the centrosymmetric tetragonal magnet EuAl 4 [49][50][51][52][53], where the importance of a spin-lattice coupling through a tetragonal-to-orthorhombic structural distortion was indicated in realizing such a low-symmetric SkX [54,55].…”