Recent experiments show that topological surface states (TSS) in topological insulators (TI) can be exploited to manipulate magnetic ordering in ferromagnets. In principle, TSS should also exist for other topological materials, but it remains unexplored as to whether such states can also be utilized to manipulate ferromagnets. Herein, current‐induced magnetization switching enabled by TSS in a non‐TI topological material, namely, a topological Dirac semimetal α‐Sn, is reported. The experiments use an α‐Sn/Ag/CoFeB trilayer structure. The magnetization in the CoFeB layer can be switched by a charge current at room temperature, without an external magnetic field. The data show that the switching is driven by the TSS of the α‐Sn layer, rather than spin‐orbit coupling in the bulk of the α‐Sn layer or current‐produced heating. The switching efficiency is as high as in TI systems. This shows that the topological Dirac semimetal α‐Sn is as promising as TI materials in terms of spintronic applications.
This article reports damping enhancement in a ferromagnetic NiFe thin film due to an adjacent α‐Sn thin film. Ferromagnetic resonance studies show that an α‐Sn film separated from a NiFe film by an ultrathin Ag spacer can cause an extra damping in the NiFe film that is three times bigger than the intrinsic damping of the NiFe film. Such an extra damping is absent in structures where the α‐Sn film interfaces directly with a NiFe film, or is replaced by a β‐Sn film. The data suggest that the extra damping is associated with topologically nontrivial surface states in the topological Dirac semimetal phase of the α‐Sn film. This work suggests that, like topological insulators, topological Dirac semimetal α‐Sn may have promising applications in spintronics.
Recently, a newly
discovered VIB group transition metal dichalcogenide
(TMD) material, 2M-WS2, has attracted extensive attention
due to its interesting physical properties such as topological superconductivity,
nodeless superconductivity, and anisotropic Majorana bound states.
However, the techniques to grow high-quality 2M-WS2 bulk
crystals and the study of their physical properties at the nanometer
scale are still limited. In this work, we report a new route to grow
high-quality 2M-WS2 single crystals and the observation
of superconductivity in its thin layers. The crystal structure of
the as-grown 2M-WS2 crystals was determined by X-ray diffraction
(XRD) and scanning tunneling microscopy (STM). The chemical composition
of the 2M-WS2 crystals was determined by energy dispersive
X-ray spectroscopy (EDS) analysis. At 77 K, we observed the spatial
variation of the local tunneling conductance (dI/dV) of the 2M-WS2 thin flakes by scanning tunneling spectroscopy
(STS). Our low temperature transport measurements demonstrate clear
signatures of superconductivity of a 25 nm-thick 2M-WS2 flake with a critical temperature (T
C) of ∼8.5 K and an upper critical field of ∼2.5 T at T = 1.5 K. Our work may pave new opportunities in studying
the topological superconductivity at the atomic scale in simple 2D
TMD materials.
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