Strongly anisotropic strain-tunability of excitons in exfoliated ZrSe$_3$

TL;DR

This study investigates how uniaxial strain affects the excitonic properties of ZrSe$_3$, revealing a highly anisotropic tunability that depends on the strain direction, supported by experimental spectroscopy and ab initio calculations.

Contribution

It demonstrates the directional dependence of exciton energy shifts under strain in ZrSe$_3$, combining experimental optical measurements with theoretical calculations for the first time.

Findings

Excitonic peaks blueshift under uniaxial tension.

Shift magnitude varies significantly with strain direction.

Experimental results agree with ab initio calculations.

Abstract

We study the effect of uniaxial strain on the band structure of ZrSe$_3$, a semiconducting material with a marked in-plane structural anisotropy. By using a modified 3-point bending test apparatus, thin ZrSe$_3$ flakes were subjected to uniaxial strain along different crystalline orientations monitoring the effect of strain on their optical properties through micro-reflectance spectroscopy. The obtained spectra showed excitonic features that blueshift upon uniaxial tension. This shift is strongly dependent on the direction along which the strain is being applied. When the flakes are strained along the b-axis, the exciton peak shifts at ~ 60-95 meV/%, while along the a-axis, the shift only reaches ~ 0-15 meV/%. Ab initio calculations were conducted to study the influence of uniaxial strain, applied along different crystal directions, on the band structure and reflectance spectra of ZrSe$_3$, exhibiting a remarkable agreement with the experimental results.