Choosing Tight-Binding Models for Accurate Optoelectronic Responses

TL;DR

This paper evaluates the accuracy of various tight-binding models in predicting the optoelectronic responses of MoS$_2$, emphasizing that matching band structures alone is insufficient for reliable optical property calculations.

Contribution

It demonstrates that both band structure and wavefunction agreement are essential for accurate optical response modeling in tight-binding approaches.

Findings

Band structure agreement alone does not ensure accurate optical responses.

Including next-nearest neighbor hoppings affects the optical response predictions.

Wavefunction accuracy is crucial for reliable optical property calculations.

Abstract

Tight-binding models provide great insight and are a low-cost alternative to \emph{ab initio} methods for calculation of a material's electronic structure. These models are used to calculate optical responses, including nonlinear optical effects such as the shift current bulk photovoltaic effect. The validity of tight-binding models is often evaluated by comparing their band structures to those calculated with Density Functional Theory. However, we find that band structure agreement is a necessary but not sufficient condition for accurate optical response calculations. In this Letter, we compute the shift current response and dielectric tensor using a variety of tight-binding models of {MoS$_2$}, including both Slater-Koster and Wannier tight-binding models that treat the Mo $4d$ orbitals and/or S $3p$ orbitals. We also truncate hoppings in the Wannier function models to next-nearest neighbor, as is common in tight-binding methods, in order to gauge the effect on optical response. By examining discrepancies in energies and optical matrix elements, we determine the interpolation quality of the different tight-binding models and establish that agreement in both band structure and wavefunctions is required to accurately model optical response,