Van der Waals twistronics in a MoS₂/WS₂ heterostructure

Twisted Van der Waals heterostructure made of two or more two-dimensional (2D) materials [1,2] has recently gained lot of interest due to the recent exploration of various strong-electron correlation effects. Here, we studied the heterostructure of MoS₂/WS₂ at different twist angles to look for exciting electronic coupling effects between the individual constituents. In this work, first-principles based density functional theory calculations [3] were used to explore the structural, electronic, mechanical and optical properties of the heterostructure at different twist angles, chosen at the minimum strain configurations. The interlayer twisting induces structural phase transition from orthorhombic => hexagonal => monoclinic symmetry. The semiconducting nature of the heterostructure changes from direct to indirect bandgap semiconductor state at different twist angles. The maximum value of optical conductivity is found to be 2000 AV^-1cm^-1 at a twist angle of 21.79^º. Our investigation showed a variation in the optical band gap value from 1.1 eV to 1.4 eV under different twisted angles. The effective mass of the electrons has a rapid variation as twist angle changes. With changing twist angle, the Poisson's ratio and shear modulus shift from 0.16 to 0.21 and 25.6 GPa to 32.1 GPa, respectively. Young's modulus and shear modulus are found to be maximum at 43.9^º angle among all the twisting angles. Also this system showed good absorption in the visible region, which can be an interesting candidate for optoelectronic applications.