Ultrahigh pyroelectricity in monoelemental 2D tellurium

TL;DR

This paper demonstrates an ultrahigh pyroelectric response in 2D tellurium nanosheets, with a coefficient significantly surpassing traditional materials, enabled by symmetry breaking and electronic state changes.

Contribution

It reports the first observation of large pyroelectricity in monoelemental 2D tellurium, revealing new mechanisms for pyroelectric enhancement in 2D materials.

Findings

Pyroelectric coefficient ~3 mC.m-2.K-1, eight times higher than PZT.

Symmetry breaking in 2D Te leads to enhanced pyroelectricity.

Surface Raman band indicates electronic state changes in 2D Te.

Abstract

We report an ultrahigh pyroelectric response in van der Waals bonded layers of two-dimensional (2D) tellurium (Te) nanosheets (thickness, d = 4 to 5 nm) at periodic on-off temperature oscillations. For the first time a large pyroelectric coefficient, Pc ~ 3 mC.m-2.K-1, is observed which is eightfold higher than the traditional state-of-the-art pyroelectrics (lead zirconate titanate, PZT). The first-principles calculations point out that the breakdown of centro-symmetry in the 1-3 Te-layers (P-3m1 space group) of a non-centrosymmetry (higher-order symmetry of C2 space group) on an angular twist in the Te-Te bonds of an exotic electronic state in 2D Te. The angular Te-Te twisting elicits a surface-enhanced Raman band at 101 cm-1 (absent in bulk Te). The stimulation of the Born effective charge, in-plane piezoelectricity and thermal expansion coefficient are shown to tailor the large pyroelectricity. Thus, 2D Te nanosheets present a new paradigm for the wide application of pyroelectric materials for developing thermal energy-based flexible electronics.