Spin field-effect transistors (SFETs) based on the Rashba effect could manipulate the spin of electrons electrically, while seeking desirable Rashba semiconductors with large Rashba constant and strong electric-field response, to preserve spin coherence remains a key challenge. Herein, we propose a series of 2D Rashba semiconductors with two-atom-thick buckled honeycomb structure (BHS) according to high-throughput first-principles density functional theory calculations. BHS semiconductors show large Rashba constants that are favorable to be integrated into nanodevices superior to conventional bulk materials, and they can be fabricated by mechanical exfoliation or chemical vapor deposition. In particular, 2D AlBi monolayer has the largest Rashba constant (2.77 eVÅ) of all 2D Rashba materials. Furthermore, 2D BiSb monolayer is a promising candidate for SFETs due to its large Rashba constant (1.94 eVÅ) and strong electric field response (0.92 eÅ2). Our designed 2D-BiSb-SFET shows shorter spin channel length (42 nm with strain) than conventional SFETs (2–5 μm).

Two-dimensional (2D) Rashba semiconductors with structure inversion asymmetry and a spin–orbit coupling (SOC) effect show promising applications in nanospintronics, such as spin field effect transistors (FETs). Here, we systematically investigate the electronic structures and Rashba effect of 2D polar perovskites ABX3 (A = Cs+ or Rb+; B = Pb2+ or Sn2+; X = Cl, Br, or I) by first-principles density functional theory calculations. We demonstrate that, except for the cubic case, 2D polar perovskites from tetragonal and orthorhombic three-dimensional (3D) bulks exhibit a strong intrinsic Rashba effect around the Γ point, due to their structure inversion asymmetry and the strong SOC effect of heavy atoms. In particular, 2D orthorhombic RbSnI3 shows the largest Rashba constant of 1.176 eV Å among these polar perovskites, which is comparable to that of 3D bulk perovskites previously reported in experiments and theory. Furthermore, several 2D polar perovskites also show a strong electric field response. In particular, 2D tetragonal RbPbI3 and tetragonal CsPbI3 have strong electric field responses of >0.5 e Å2. Therefore, 2D polar perovskites as promising Rashba semiconductors possess large Rashba constants and strong electric field responses, resulting in a short spin channel length of tens of nanometers to preserve the spin coherence in spin FETs, superior to conventional 3D micrometer spin FETs.

This theoretical Perspective reviews spin−orbit coupling (SOC), including the Rashba effect and Dresselhaus effect, in two-dimensional (2D) semiconductors. We first introduce the origin of the Rashba effect and Dresselhaus effect using the Hamiltonian models; we then summarize 2D Rashba semiconductors predicted by first-principles density functional theory (DFT) calculations, including AB binary monolayers, Janus monolayers, 2D perovskites, and so on. We also review various manipulating techniques of the Rashba effect on 2D semiconductors, such as external electric field, strain engineering, charge doping, interlayer interactions, proximity effect of substrates, and external magnetic field. We then briefly summarize the applications of SOC, including the generation, detection, and manipulation of spin currents in spin Hall effect transistors and spin field effect transistors. Finally, we conclude this Perspective and propose three promising research fields of SOC in low-dimensional semiconductors, including the nonlinear SOC Hamiltonian model, 2D ferroelectric SOC semiconductors, and 1D Rashba model and semiconductors. This theoretical Perspective enriches the fundamental understanding of SOC in 2D semiconductors and will help in the design of new types of spintronic devices in future experiments.

A long-standing goal in spintronics is electric control of spin. Herein, we perform an inverse design to search for 2D ferroelectric Rashba semiconductors, whose spin texture can be precisely and readily reversed by switching ferroelectric polarization via the electric field. The inverse design involves defining and utilizing the design principles of the Rashba effect and ferroelectricity. After screening materials from a database based on the enabling design principles, we identify three potential types of structure that simultaneously possess the Rashba effect and ferroelectricity, including A 2 P 2 X 6 type (space group P31m), ABP 2 X 6 type (space group P3), and AB type (space group P3m1). By performing high-throughput density functional theory calculations of three types of structure and material screening by the optimizing design principles, we find that 14 AB monolayers are promising 2D ferroelectric Rashba semiconductors due to their pure Rashba effect in the conduction band minimum, thinnest 2D Rashba structure, and surmountable energy barriers for ferroelectric polarization. The electrically reversible spin texture makes ferroelectric Rashba semiconductors promising candidates for next-generation spintronics in the future.