Stretching ReS2 along different crystal directions: Anisotropic tuning of the vibrational and optical responses

Rhenium disulfide (ReS2) is a semiconducting two-dimensional material with marked in-plane structural anisotropy. This lattice anisotropy is the stem of many quasi-1D properties observed in this material. In this work, we focus on strain engineering of optical and vibrational properties through mechanical deformations of the lattice. In particular, the exciton energy can be shifted by applying uniaxial strain, and the gauge factor is six times more pronounced when the strain is applied along the b-axis than in perpendicular to the b-axis of the ReS2 lattice. Moreover, we also observed how the two most prominent Raman modes can be shifted by uniaxial strain, and the shift strongly depends on the alignment between the uniaxial strain direction and the a- and b-axes of the ReS2 lattice.