posted on 2024-01-22, 16:43authored byYilimiranmu Rouzhahong, Chao Liang, Jian He, Xinyi Lin, Biao Wang, Huashan Li
Piezoelectricity has been widely explored for nanoelectromechanical
applications, yet its working modes are mainly limited in polar directions.
Here we discover the intrinsic electro-mechanical response in crystal
materials that is transverse to the conventional polarized direction,
which is named unconventional piezoelectricity. A Hall-like mechanism
is proposed to interpret unconventional piezoelectricity as charge
polarization driven by a built-in electric field for systems with
asymmetric Berry curvature distributions. Density functional theory
simulations and statistical analyses justify such a mechanism and
confirm that unconventional piezoelectricity is a general property
for various two-dimensional materials with spin splitting or valley
splitting. An empirical formula is derived to connect the conventional
and unconventional piezoelectricity. The extended understanding of
the piezoelectric tensor in quantum materials opens an opportunity
for applications in multidirectional energy conversion, broadband
operation, and multifunctional sensing.