Valley Piezoelectric Mechanism for Interpreting and Optimizing Piezoelectricity in Quantum Materials via Anomalous Hall Effect

TL;DR

This paper introduces the valley piezoelectric mechanism driven by the Valley Hall effect, providing a new theoretical framework to enhance piezoelectricity in quantum materials by leveraging quantum effects and external strategies.

Contribution

The study develops a novel valley piezoelectric model based on the Valley Hall effect, validated by calculations, and proposes strategies to significantly improve piezoelectricity in quantum materials.

Findings

Valley piezoelectricity depends on valley splitting, hybridization, bandgap, and Poisson ratio.

DFT simulations show over 130% increase in piezoelectricity through optimization strategies.

The model links quantum effects with electro-mechanical responses in materials.

Abstract

Quantum materials have exhibited attractive electro-mechanical responses, but their piezoelectric coefficients are far from satisfactory due to the lack of fundamental mechanisms to benefit from the quantum effects. We discovered the valley piezoelectric mechanism that is absent in traditional piezoelectric theory yet promising to overcome this challenge. A theoretical model was developed to elucidate the valley piezoelectricity as the Valley Hall effect driven by pseudoelectric field, which can be significant in quantum systems with broken time reversal symmetry. Consistent tight-binding and density-functional-theory (DFT) calculations validate the model and unveil the crucial dependence of valley piezoelectricity on valley splitting, hybridization energy, bandgap, and Poisson ratio. Doping, passivation, and external stress are proposed as rational strategies to optimize piezoelectricity, with a more than 130% increase of piezoelectricity demonstrated by DFT simulations. The general valley piezoelectric model bridges the gap between electro-mechanical response and quantum effects, which opens an opportunity to achieve outstanding piezoelectricity in quantum materials via optimizing spin-valley and spin-orbit couplings.