Tunable ferroelectricity and anisotropic electric transport in monolayer $\beta$-GeSe

TL;DR

This study predicts and demonstrates tunable in-plane ferroelectricity and anisotropic electric transport in monolayer β-GeSe, with properties controllable by strain, making it promising for 2D ferroelectric and nanoelectronic applications.

Contribution

First-principles calculations reveal ferroelectricity and strain-tunable properties in monolayer β-GeSe, a newly synthesized 2D material with potential device applications.

Findings

Spontaneous in-plane polarization of about 0.16 nC/m.

Curie temperature can be increased above room temperature with strain.

Strain can rotate the preferred conduction direction by 90°.

Abstract

Low-dimensional ferroelectricity has attracted tremendous attention due to its huge potential in device applications. Here, based on first-principles calculations, we predict the existence of spontaneous in-plane electrical polarization and ferroelectricity in monolayer $\beta$-GeSe, a polymorph of GeSe with a boat conformation newly synthesized in experiment. The magnitude of the polarization is about $0.16$ nC/m, which is comparable to that of monolayer SnTe studied in recent experiment, and the intrinsic Curie temperature is estimated to be above 200 K. Interestingly, owing to its puckered structure, the physical properties of $\beta$-GeSe can be easily controlled by strain. The Curie temperature can be raised above room temperature by applying a ($\sim 1\%$) tensile strain, and the magnitude of polarization can be largely increased by strains in either armchair or zigzag directions. Furthermore, we find that for the case with electron doping, applying strain can readily tune the anisotropic electric transport with the preferred conducting direction rotated by $90^\circ$, which is connected with a strain-induced Lifshitz transition. The ratio between the effective masses along the two in-plane directions can undergo a dramatic change of two orders of magnitude even by a 2% strain. Our result reveals monolayer $\beta$-GeSe as a promising platform for exploring ferroelectricity in two-dimensions and for nanoscale mechano-electronic device applications.