# Disentangling bulk and surface Rashba effects in ferroelectric ${\alpha}$-GeTe

Krempaský, J; Volfová, H; Muff, S; Pilet, N; Landolt, G; Radović, M; Shi, M; Kriegner, D; Holý, V; Braun, J; Ebert, H; Bisti, F; Rogalev, V A; Strocov, V N; Springholz, G; Minár, J; Dil, J H (2016). Disentangling bulk and surface Rashba effects in ferroelectric ${\alpha}$-GeTe. Physical Review B, 94(20):205111.

## Abstract

Macroscopic ferroelectric order in ${\alpha}$-GeTe with its noncentrosymmetric lattice structure leads to a giant Rashba spin splitting in the bulk bands due to strong spin-orbit interaction. Direct measurements of the bulk band structure using soft x-ray angle-resolved photoemission (ARPES) reveals the three-dimensional electronic structure with spindle torus shape. By combining high-resolution and spin-resolved ARPES as well as photoemission calculations, the bulk electronic structure is disentangled from the two-dimensional surface electronic structure by means of surface capping, which quenches the complex surface electronic structure. This unravels the bulk Rashba-split states in the ferroelectric Rashba ${\alpha}$-GeTe(111) semiconductor exhibiting a giant spin splitting with Rashba parameter ${\alpha}$R around 4.2 eV Å, the highest of so-far known materials.

## Abstract

Macroscopic ferroelectric order in ${\alpha}$-GeTe with its noncentrosymmetric lattice structure leads to a giant Rashba spin splitting in the bulk bands due to strong spin-orbit interaction. Direct measurements of the bulk band structure using soft x-ray angle-resolved photoemission (ARPES) reveals the three-dimensional electronic structure with spindle torus shape. By combining high-resolution and spin-resolved ARPES as well as photoemission calculations, the bulk electronic structure is disentangled from the two-dimensional surface electronic structure by means of surface capping, which quenches the complex surface electronic structure. This unravels the bulk Rashba-split states in the ferroelectric Rashba ${\alpha}$-GeTe(111) semiconductor exhibiting a giant spin splitting with Rashba parameter ${\alpha}$R around 4.2 eV Å, the highest of so-far known materials.

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