Strain-induced gyrotropic effects in ferroelectric BaTiS3

TL;DR

This study predicts strain-induced phase transitions in BaTiS3 that enhance or activate gyrotropic effects like optical activity and anomalous Hall effect, making it promising for advanced optical and transport devices.

Contribution

It is the first to theoretically demonstrate strain-controlled phase transitions and gyrotropic effects in BaTiS3, linking structural changes to optical and electronic properties.

Findings

Tensile strain induces a symmetry-lowering phase transition enhancing optical activity.

Compressive strain activates the nonlinear anomalous Hall effect and causes sign reversal.

Multiple phase transitions under strain lead to large gyrotropic responses.

Abstract

Gyrotropic effects, including natural optical activity (NOA) and the nonlinear anomalous Hall effect (NAHE), are crucial for advancing optical and transport devices. We explore these effects in the BaTiS3 system, a quasi-one-dimensional crystal that exhibits giant optical anisotropy. (Niu et al. Nat. Photonics 12, 392 (2018); Zhao et al. Chem. Mater. 34, 5680 (2022)). In the P63cm phase which is stable under room temperature, we predict two distinct strain-induced phase transitions: a symmetry-lowering transition from the P63cm to P63 phase under tensile strain, which enhances NOA and enables optical rotation; and an isostructural insulator-to-polar Weyl semimetal (WSM) transition under compressive strain, which activates the NAHE and exhibits a strain-induced sign reversal. The low-temperature P21 phase also transforms into a P212121 phase under enough compressive strains with such phase transition exhibiting a large NOA. All these results highlight BaTiS3 as a viable candidate for novel ferroelectrics, optical and transport devices with strain enhanced or activated gyrotropic properties.