Topological Hall effect in Dirac semimetal

Magnetic skyrmions are chiral spin textures whose non-trivial real space topology is often created by an interfacial anisotropic Dzyaloshinkii-Moriya exchange interaction (DMI) that originates from spin-orbit coupling and broken inversion symmetry [1]. We investigated the formation of skyrmions at the interface of a canonical DSM (Cd₃As₂) and a ferromagnetic semiconductor (In_1-xMn_xAs) with perpendicular magnetic anisotropy. Our calculations indicate nonzero spin susceptibility in such heterostructures due to Rashba spin-orbit coupling from broken inversion symmetry, implying the DM interaction necessary for skyrmions. To experimentally test this idea, we grew Cd₃As₂/In_1-xMn_xAs bilayers and mapped out the behavior of the Hall effect as a function of temperature, magnetic field, and gate voltage in electrostatically top gated devices. Below T = 6 K, we observe an emergent gate-tunable topological Hall effect (THE) indicated by an excess Hall resistance [2]. This signature is most pronounced at the charge neutrality point, suggesting the formation of a Dirac-electron mediated chiral spin texture at the DSM/ferromagnet interface. Our study provides a new platform to study the interplay between the topological states in DSMs and the chiral spin textures associated with the THE.

References:

[1] A. Fert, N. Reyren, and V. Cros, Nat. Rev. Mater., 2, 1 (2017)

[2] S. Islam et al., under preparation