Abstract
Spin–orbit torque has recently been intensively investigated for the purposes of manipulating the magnetization in magnetic nano-devices and understanding fundamental physics. Therefore, the search for novel materials or material combinations that exhibit a strong enough spin-torque effect has become one of the top priorities in this field of spintronics. Weyl semimetal, a new topological material that features open Fermi arc with strong spin–orbit coupling and spin–momentum locking effect, is naturally expected to exhibit an enhanced spin-torque effect in magnetic nano-devices. Here we observe a significantly enhanced spin conductivity, which is associated with the field-like torque at low temperatures. The enhancement is obtained in the b-axis WTe2/Py bilayers of nano-devices but not observed in the a-axis of WTe2/Py nano-devices, which can be ascribed to the enhanced spin accumulation by the spin–momentum locking effect of the Fermi arcs of the Weyl semimetal WTe2.
Highlights
Spin–orbit torque has recently been intensively investigated for the purposes of manipulating the magnetization in magnetic nano-devices and understanding fundamental physics
Owing to the existence of strong spin–orbit coupling (SOC) in topological materials[4,5], such as topological insulators, the magnetic heterostructures composed of topological materials have received significant attention for both their potential to advance the fundamental understanding of the underlying physics and possible applications[6,7,8]
An out-of-plane damping-like (DL) torque induced by broken inversion symmetry was observed in the WTe2/Py heterostructures at room temperature[26,27], the spin–orbit torques originating from the topological Fermi arc remain undiscovered
Summary
Spin–orbit torque has recently been intensively investigated for the purposes of manipulating the magnetization in magnetic nano-devices and understanding fundamental physics. A new topological material that features open Fermi arc with strong spin–orbit coupling and spin–momentum locking effect, is naturally expected to exhibit an enhanced spin-torque effect in magnetic nano-devices. A number of intriguing properties have been observed in these topological semimetals, such as high carrier mobility, extremely large magnetoresistance (MR), and, especially, the existence of surface states (i.e., the Fermi arcs at the surfaces of the sample) These Fermi arcs are robust against scattering, which should lead to interesting properties in the magnetic heterostructures composed of Dirac and Weyl topological semimetals. It has been predicted and experimentally demonstrated that WTe2 is a type-II Weyl semimetal[28,29,30] in which the Weyl points occur at the crossing of the oblique conduction and the valence bands due to the broken inversion symmetry[23]. We demonstrate that the topological Fermi arcs of WTe2 are along the Y-direction (b-axis) and that the spin–momentum locking effect enhances the fieldlike (FL) torques of the WTe2/Py bilayers at low temperatures
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