High harmonic generation in crystals using maximally localized Wannier functions

TLDR: In this article, the authors proposed the use of the maximally localized Wannier functions that provide a framework to map ab initio calculations to an effective tight-binding Hamiltonian with great accuracy.

Abstract: In this work, the nonlinear optical response, and in particular, the high harmonic generation of semiconductors, is addressed by using the Wannier gauge. One of the main problems in the time evolution of the Semiconductor Bloch equations resides in the fact that the dipole couplings between different bands can diverge and have a random phase along the reciprocal space, and this leads to numerical instability. To address this problem, we propose the use of the maximally localized Wannier functions that provide a framework to map ab initio calculations to an effective tight-binding Hamiltonian with great accuracy. We show that working in the Wannier gauge, the basis set in which the Bloch functions are constructed directly from the Wannier functions, the dipole couplings become smooth along the reciprocal space, thus avoiding the problem of random phases. High harmonic generation is computed for a two-dimensional monolayer of hexagonal boron nitride as a numerical demonstration.