Enhancement of Zener tunneling rate via electron-hole attraction within a time-dependent quasi-Hartree-Fock method

TL;DR

This paper introduces a quasi-Hartree-Fock method to study how electron-hole attraction influences Zener tunneling rates under strong electric fields, revealing significant enhancement effects across different materials.

Contribution

The development of a flexible quasi-Hartree-Fock framework that independently adjusts electronic structure parameters and electron-hole interaction strength for analyzing tunneling phenomena.

Findings

Electron-hole attraction increases tunneling rates in all studied systems.

Strong electron-hole interactions lead to several-fold tunneling rate enhancements.

Weak interactions result in tens of percent increase in tunneling rates.

Abstract

The tunneling process, a prototypical phenomenon of nonperturbative dynamics, is a natural consequence of photocarrier generation in materials irradiated by a strong laser. Common treatments for Zener tunneling are based on a one-body problem with a field-free electronic structure. In a literature (Ikemachi et al., Phys. Rev. A 98, 023415 (2018)), a characteristic of gap shrinking or excitation can occur due to the electron-hole interaction for slow and strong time-varying electric fields. We have developed a theoretical framework called the quasi-Hartree-Fock (qHF) method to enable a more flexible imitation of the electronic structures and electron-hole attraction strength of materials compared to the original Hartree-Fock method. In the qHF framework, band gap, reduced effective mass, and electron-hole interaction strength can be independently selected to reproduce common crystals. In this study, we investigate the effect of electron-hole attraction on Zener tunneling subjected to a DC electric field for four different systems using the qHF method. Our findings demonstrate that the electron-hole attraction promotes the tunneling rates in all four material systems assumed as examples. Specifically, systems that have a strong electron-hole interaction show a few factor enhancements for tunneling rates under DC fields, while systems with a weak interaction show higher enhancements of a few tens of percent.