# Maximal Rashba Splitting in GeTe/Bi2Te3 Heterostructures via Strong Band Bending

## TL;DR

This paper shows how combining GeTe and Bi2Te3 in a heterostructure creates a strong Rashba effect, useful for spintronic devices.

## Contribution

A new method to achieve maximal Rashba splitting via strong band bending in GeTe/Bi2Te3 heterostructures is demonstrated.

## Key findings

- A Rashba parameter of αR=6.86±0.59 eV·Å is achieved in GeTe/Bi2Te3 heterostructures.
- Strong band bending at the interface is identified as the origin of the enhanced Rashba effect.
- The Rashba effect increases as the thickness of GeTe decreases.

## Abstract

The Rashba effect has emerged as a pivotal phenomenon driving novel discoveries in condensed matter physics. Materials with large Rashba energy E
R, wavenumber offset k
0 and Rashba parameter αR are prerequisites for spintronic devices operating above room temperature. While neither ultrathin GeTe films (<3.0 nm thickness) nor monolayer topological insulator Bi2Te3 (1 quintuple layer (QL) on Si(111)) manifest Rashba splitting, An unprecedented strength of Rashba effect with ER=0.57±0.03eV, k0=0.16±0.03Å−1 and αR=6.86±0.59eV·Å in GeTe (1 nm)/Bi2Te3 (1 QL) heterostructure is achieved. The spin‐momentum‐locked bands resulting from the Rashba effect of GeTe /Bi2Te3 is confirmed by density functional theory (DFT) calculations. In GeTe (x nm)/Bi2Te3(10 QL), it is find that the values of E
R, k
0 and αR significantly enhance as the thickness of GeTe decreases contrasting with GeTe films. By comparing the thickness dependence of GeTe with that of GeTe/Bi2Te3, it is determined that the enhanced Rashba parameter Δα
R
is proportional to the electric field in the GeTe/Bi2Te3 heterojunction region. It is concluded that the origin of this huge Rashba effect is attributed to the strong band bending in the GeTe/Bi2Te3 heterojunction region, where the striking inversion‐symmetry‐breaking and significant bandgap difference result in a sharp potential gradient normal to the interface. This work opens an avenue to enhance the Rashba splitting by strong band bending and design spin field effect transistors with spin channel as short as several nanometer scales.

An unprecedented strength of Rashba effect with E
R = 0.57 eV, k0=0.16Å−1 and αR=6.86eV·Å in GeTe (1 nm)/Bi2Te3 (1 QL) heterostructure. The enhanced Rashba is origined from the band bending effect in the heterojunction region of GeTe /Bi2Te3 heterostructure, which caused by charge transfer.