Simulation of ac conductivity of monolayer MoS₂ at terahertz frequencies

In conventional time-dependent device simulation, an electronic transport solver is usually coupled with a quasi-electrostatic Poisson’s equation solver in order to incorporate field effects. However, at THz frequencies, the quasi-electrostatic approximation is no longer accurate. Thus, a deeper understanding of carrier–field interaction is needed to model carrier transport under the influence of ac electromagnetic fields.

At the NUSOD-22 conference, we will discuss about our computational tool for the frequency-dependent low-field conductivity of monolayer MoS₂ in the terahertz range, where no interband transitions are possible. Our numerical simulation tool combines the ensemble Monte Carlo (EMC) technique for describing diffusive carrier transport with the finite-difference-time-domain (FDTD) technique for solving Maxwell’s curl equations. The tool is useful for numerical characterization of MoS₂ for determining the values of experimental parameters that are hard to measure directly. Furthermore, the technique can be readily extended to predict the terahertz conductivity of other promising TMDs and 2D materials.

Three-dimensional (3D) simulation geometry. A TEM wave is used to excite the MoS₂ layer. The four vertical boundary planes are terminated by periodic boundary conditions, while the top and bottom boundaries have convolutional perfectly matched layer (CPML) absorbing boundary conditions.