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Paper IPM / P / 16771  


Abstract:  
Magnetic Weyl semimetals are unique among topological materials in possessing magnetic textures that are embedded directly into their topological structure and interact dynamically with it. The resulting interplay between nontrivial realspace and momentumspace topologies makes magnetic Weyl semimetals prominent candidates for the electrical manipulation of magnetic textures, with electrical control of local domain walls potentially enabling faster, lower power manipulation than conventional ferromagnetic metals. Since the magnetization, which is in general inhomogeneous, determines the location of the Weyl nodes, we demonstrate here that nonequilibrium carrier dynamics in the vicinity of the Weyl nodes in turn influences the magnetization, leading to a nodal spintransfer torque (NSTT) facilitated by charge accumulation on either side of a domain wall, with no counterpart in other materials. Using the LandauLifshitzGilbert equation we show that the nodal spintransfer torque in real space results from the displacement of the Weyl nodes in momentum space mediated by the electricallydriven inhomogeneous magnetic texture, and is directly responsible for an electric fieldinduced structural transition in the magnetic configuration of onedimensional domain walls and threedimensional ferromagnetic domains. Remarkably, specific electric field orientations cause a Néel domain wall to vanish entirely, whereas a Bloch domain wall survives as the magnetization on either side of it is rotated. In order to examine the associated charge dynamics we develop a quantum kinetic theory for magnetic Weyl semimetals with dynamical domain walls under the influence of an external electric field, which captures the interplay between the driving force on the charge carriers, momentumspace topology and the realspace magnetic texture. We demonstrate that the presence of domain walls leads to nonlinear anomalous drift and Hall currents, whose realspace profile can be used as a probe of the steadystate magnetic texture. For certain electric field orientations an electrical chiral anomaly emerges, accompanied by the accumulation of extrinsic anomalous charge across the domain walls. We discuss experimental observation in stateofthe art samples and implications for magnetic memory and computing devices.
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