Magnetic field-induced non-trivial electronic topology in Fe3−xGeTe2

• DOI: 10.1063/5.0052952
• Publication Date: 2021-10-07T13:49:07Z
• Authors: Juan Macy; Danilo Ratkovski; Purnima P. Balakr...; Mara Strungaru; Yu-Che Chiu; Aikaterini Flessa...; Alex Moon; Wenkai Zheng; Ashley Weiland; Gregory T. McCand...; Julia Y. Chan; Govind S. Kumar; Michael Shatruk; Alexander J. Grutter; Julie A. Borchers; William D. Ratcliff; Eun Sang Choi; Elton J. G. Santos; Luis Balicas
• Keywords: Nernst effect; Skyrmion; Magnetic structure

The anomalous Hall, Nernst and thermal Hall coefficients of Fe$_{3-x}$GeTe$_2$ display several features upon cooling, like a reversal in the signal below $T = 50$ K pointing to topological transition (TT) associated development magnetic spin textures. Since transport variables are related Berry curvature, possible TT might imply deviations from Wiedemann-Franz (WF) law. However, found, within our experimental accuracy, satisfy WF law for magnetic-fields $\mu_0H$ applied along its inter-layer direction. Surprisingly, large also observed planar \emph{a}-axis as well gradient chemical potential, configuration that should not lead their observation due absence Lorentz force. $\|$ is increased, magnetization neutron scattering indicate just progressive canting moments towards planes followed by saturation. These quantities found scale with component ($M_{\|}$), showing instead sharp decrease beyond $\sim \mu_0 H_{\|} $ 4 T which field required align $\mu_0 H_{\|}$. We argue locally chiral structures, such skyrmions, possibly skyrmion tubes, dependent spin-chirality hence novel type transport. Locally spin-structures captured Monte-Carlo simulations incorporating small Dzyaloshinskii-Moriya biquadratic exchange interactions.