Tunable Rashba spin splitting in Janus transition-metal dichalcogenide monolayersviacharge doping

Abstract

Two-dimensional (2D) Janus transition-metal dichalcogenides (TMDs) (MXY, M ¼ Mo, W; X, Y ¼ S, Se, Te; X s Y) have desirable energy gaps and high stability in ambient conditions, similar to traditional 2D TMDs with potential applications in electronics. But different from traditional 2D TMDs, 2D Janus TMDs possess intrinsic Rashba spin splitting due to out-of-plane mirror symmetry breaking, with promising applications in spintronics. Here we demonstrate a new and effective way to manipulate the Rashba effect in 2D Janus TMDs, that is, charge doping, by using first-principles density functional theory (DFT) calculations.We find that electron doping can effectively strengthen the Rashba spin splitting at the valence band maximum (VBM) and conduction band minimum (CBM) in 2D Janus TMDs without constant energy consumption, superior to traditional techniques (electric fields and strain engineering), but hole doping would weaken the Rashba effect in 2D Janus TMDs. By combining the DFT calculations with the electric-triple-layer model, we also reveal the intrinsic mechanism of tuning the Rashba effect in 2D Janus TMDs by charge doping, and find that the charge transfer plays an important role in tuning the Rashba spin splitting in 2D polar semiconductors. In particular, the Rashba constants are linearly dependent on the charge transfer between X (or Y) and M atoms in 2D Janus TMDs. These results enrich the fundamental understanding of the Rashba effect in 2D semiconductors, which can be promising candidates for spin field-effect transistors (FETs) in experiments. Recently, a polar TMD monolayer, MoSSe, has been successfully synthesized in experiments, 17,18 and is a Janus TMD. 2D Janus TMD monolayers MXY (M ¼ Mo, W; X, Y ¼ S, Se, Te; X s Y) show desirable energy gaps (1.0-2.0 eV) 19,20 and high stability [17][18][19][20] in ambient conditions, similar to traditional 2D TMDs 21-23 with potential applications in electronics. In particular, the Janus TMD monolayers show intrinsic Rashba spin splitting due to the

Manipulable Electronic and Optical Properties of Two-Dimensional MoSTe/MoGe2N4 van der Waals Heterostructures

“…One layer of the halogen atom X in MX 2 can be replaced by another halogen atom Y, which can form a non-centrosymmetric structure and is referred to as Janus materials with the chemical formula Janus MXY [11,12]. Janus MXY have many unique physical properties that distinguish them from conventional 2D materials, including strong in-plane piezoelectric polarization [13], valley splitting [14], Rashba spin splitting [15,16], and good catalytic properties [17]. In recent years, people have conducted a lot of research on Janus MXY for M = Mo, W and X, Y = S, Se, Te, etc.…”

2D Janus Transition Metal Dichalcogenides: Properties and Applications

“…Moreover, the Rashba effect could be controlled by external strain, EF, and charge doping. [ 30,34–36 ] For instance, in WSeTe, it is observed that a small strain (−2%−2%) can substantially change the Rashba SOC (−50%−50%) by modulating the W–Se interaction. The orbital selective external potential method further revealed that the change of W‐ and Se‐ p z orbital overlap played a key role in controlling the Rashba SOC.…”

Recent advances in low-dimensional Janus materials: theoretical and simulation perspectives

“…Other methods can be also used to manipulate the Rashba effect. Chen et al [109] explored by firstprinciples calculations the use of charge doping as a strategy to manipulate the Rashba effect in 2D Janus TMDs. The authors found that electron doping can strengthen the Rashba spin splitting at the valence band maximum (VBM) and conduction band minimum (CBM) of 2D Janus TMDs without constant energy consumption, as required by traditional techniques (electric fields and strain engineering).…”