Strongly Anisotropic Strain-Tunability of Excitons in Exfoliated ZrSe₃.

[EN] The effect of uniaxial strain on the band structure of ZrSe3 , a semiconducting material with a marked in-plane structural anisotropy, is studied. By using a modified three-point bending test apparatus, thin ZrSe3 flakes are subjected to uniaxial strain along different crystalline orientations monitoring the effect of strain on their optical properties through micro-reflectance spectroscopy. The obtained spectra show 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 %-1 , while along the a-axis, the shift only reaches 0-15 meV %-1 . Ab initio calculations are conducted to study the influence of uniaxial strain, applied along different crystal directions, on the band structure and reflectance spectra of ZrSe3 , exhibiting a remarkable agreement with the experimental results.his project was funded from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (grant agreement no. 755655, ERC-StG 2017 project 2D-TOPSENSE). R.F. acknowledges the support from the Spanish Ministry of Economy, Industry and Competitiveness through a Juan de la Cierva-formación fellowship 2017 FJCI2017-32919. R.D. acknowledges the financial support of the Grupos Consolidados del Gobierno Basco (Grant IT1249-19) and the MINECO (Grant G17/A01). G.S.-S. acknowledges financial support from Spanish MICIU RTI2018-099054-J-I00 and MICINN IJC2018-038164-I. Electron microscopy observations were carried out at the Centro Nacional de Microscopia Electronica, CNME-UCM. R.D. also acknowledges useful discussions with D. Varsano. H.L. acknowledges the grant from China Scholarship Council (CSC) under no. 201907040070. The authors extend their sincere appreciation to the Distinguished Scientist Fellowship Program (DSFP) at King Saud University for funding of this work