Intrinsic spin Nernst effect of magnons in a noncollinear antiferromagnet

Abstract

We investigate the intrinsic magnon spin current in a noncollinear antiferromagnetic insulator. The spin current is in general found to be non-conserved, but for certain symmetries and spin polarizations, the averaged effect of non-conserving terms can vanish. We formulate a general linear response theory for magnons in noncollinear antiferromagnets subject to a temperature gradient and analyze the effect of symmetries on the response tensor. We apply this theory to single-layer potassium iron jarosite KFe3(OH)6(SO4)2 and predict a measurable spin current response. arXiv:1907.10567v2 [cond-mat.mes-hall]

A Perspective on Magnon Spin Nernst Effect in Antiferromagnets

“…In Ref. 34 , the out-of-plane polarized SNE is weaker than in-plane polarized SNE, while in Ref. 33 the out-of-plane component is not visible in simulation.…”

“…For example, KFe 3 (OH) 6 (SO 4 ) 2 has a Kagome lattice with in-plane 120 • spin alignment. A single layer sample can exhibit the magnon SNE 33,34 . However, different from the collinear case, the magnon spin polarization in a noncollinear Kagome magnet can be either out-of-plane or in-plane, leading to two kinds of magnon SNE.…”

“…While the magnon SNE in noncollinear magnets still originates from the Berry curvature, the underlying topological structure is more complicated than that of the collinear magnets. There are three magnon bands in a noncollinear Kagome magnet consisting of three distinct sublattices, where the band Chern numbers are -3, 1 and 2 34 . Furthermore, the DM interaction is believed to induce an out-of-plane canting of spins, which gives rise to a small net magnetization in the ground state.…”

Magnetoelastic coupling enabled tunability of magnon spin current generation in 2D antiferromagnets

“…For this purpose, a generalized Berry curvature should be defined for operator θ = 1 4 (S z φv + v φS z ) where v = −1 ∂ k H is the velocity operator and S z = − N/2 i λ i a † i a i is the magnon spin operator. The generalized Berry curvature of the nth band is given by [47] (…”

Spin superfluidity in noncollinear antiferromagnets

“…The noncollinear conducting magnets can exhibit a multitude of phenomena associated with topology of electronic bands [21], e.g., Mn 3 X (X = Ge, Sn, Ga, Ir, Rh, or Pt) magnets exhibit the anomalous [22] and spin [23] Hall responses. Various magnon-mediated responses relying on magnon spin-momentum locking, topology of magnonic bands, and coupling to phonons have been studied theoretically, promising observation of spin-related phenomena in insulating antiferromagnets [24][25][26][27][28][29][30][31][32].…”