Effects of strain-tunable valleys on charge transport in bismuth

TL;DR

This study investigates how externally applied strain influences charge transport in bulk bismuth by tuning valley populations, revealing strain-dependent changes in elastoresistance and valley density, crucial for valleytronics device design.

Contribution

It demonstrates the controllable manipulation of valley populations in bulk bismuth through external strain, combining experimental measurements and first-principle calculations.

Findings

Elastoresistance exhibits both antisymmetric and symmetric responses with temperature.

Strain significantly alters valley density as shown by quantum oscillations.

First-principle calculations confirm strain-induced changes in band structure.

Abstract

The manipulation of the valley degree of freedom can boost the technological development of novel functional devices based on valleytronics. The current mainstream platform for valleytronics is to produce a monolayer with inversion asymmetry, in which the strain-band engineering through the substrates can serve to improve the performance of valley-based devices. However, pinpointing the effective role of strain is inevitable for the precise design of the desired valley structure. Here, we demonstrate the charge transport under continuously controllable external strain for bulk bismuth crystals with three equivalent electron valleys and one hole valley. The strain response of resistance, namely elastoresistance, exhibits the evolutions in both antisymmetric and symmetric channels with decreasing temperature. The elastoresistance behaviors mainly reflect the significant changes in valley density depending on the symmetry of induced strain, evidenced by our strain-dependent quantum oscillation measurements and first-principle band calculations under strain. These facts suggest the successful tune and evaluation of the valley populations through strain-dependent charge valley transport.