Ferroelectric Control of the Spin Texture in GeTe

Abstract

The electric and nonvolatile control of the spin texture in semiconductors would represent a fundamental step toward novel electronic devices combining memory and computing functionalities. Recently, GeTe has been theoretically proposed as the father compound of a new class of materials, namely ferroelectric Rashba semiconductors. They display bulk bands with giant Rashba-like splitting due to the inversion symmetry breaking arising from the ferroelectric polarization, thus allowing for the ferroelectric control of the spin. Here, we provide the experimental demonstration of the correlation between ferroelectricity and spin texture. A surface-engineering strategy is used to set two opposite predefined uniform ferroelectric polarizations, inward and outward, as monitored by piezoresponse force microscopy. Spin and angular resolved photoemission experiments show that these GeTe(111) surfaces display opposite sense of circulation of spin in bulk Rashba bands. Furthermore, we demonstrate the crafting of nonvolatile ferroelectric patterns in GeTe films at the nanoscale by using the conductive tip of an atomic force microscope. Based on the intimate link between ferroelectric polarization and spin in GeTe, ferroelectric patterning paves the way to the investigation of devices with engineered spin configurations.

Spin Hall effect in prototype Rashba ferroelectrics GeTe and SnTe

“…Both possess spontaneous electric polarization P parallel to [111] direction, but the high Curie temperature of GeTe (T C = 700 K) 12,13 allowed in-depth experimental studies of the ferroelectric phase which proved the polarization switching, 14 electronic structures [15][16][17] and reversible Rashba spin textures. 18 Importantly, spinto-charge conversion has been recently measured via spin pumping experiments in Fe/GeTe bilayers demonstrating high potential of such interfaces for multifunctional spintronics applications. 19,20 On the other hand, ferroelectric phase of SnTe (T C = 100 K) 21 has been known mainly from the theoretical side.…”

Band splitting with vanishing spin polarizations in noncentrosymmetric crystals

“…1. Even though the Rashba effect is generally associated to heterostructures and surfaces, as due to 2D structural inversion asymmetry, a giant Rashba effect has been recently observed in bulk polar/ferroelectric systems [19][20][21][22][23] . Sometimes, Dresselhaus and Rashba terms coexist 24 , giving rise to interesting physics and novel applications.…”

Infrared photovoltaic detector based on p-GeTe/n-Si heterojunction

“…It has been considered as a strong contender for the next-generation memory technology as the material exhibits different physical, electrical and optical properties when it is in amorphous and crystal phases [16][17][18][19][20][21]. GeTe can also be made into dilute magnetic semiconductor, which is an important material for spintronics devices [15,22,23]. If the unique storage and computing features of GeTe can be integrated to develop novel devices, this will lead to significant advancement in the computing technology.…”