Shift current in 2D Janus Transition-Metal Dichalcogenides: the role of excitons

TL;DR

This paper explores how excitons influence the shift current in 2D Janus TMDs, revealing enhanced photocurrent due to electron-hole localization and displacement, with implications for optoelectronic applications.

Contribution

It introduces a real-time approach incorporating many-body effects to analyze exciton-enhanced shift current in Janus TMDs, highlighting their potential for energy-harvesting devices.

Findings

Shift current is strongly enhanced by C excitons.

Electron and hole are localized on different atoms, causing charge displacement.

Janus TMDs are promising for next-generation photovoltaic technologies.

Abstract

We investigate the shift current in two-dimensional (2D) Janus transition-metal dichalcogenides (TMDs). The shift current is evaluated using a real-time approach, where the coupling with an external field is described in terms of a dynamical Berry phase. This methodology incorporates electron-hole interactions and quasiparticle band structure renormalization through an effective Hamiltonian derived from many-body perturbation theory. We find that the shift current is strongly enhanced in correspondence with C excitons. An analysis in terms of the electron-hole pairs reveals that electron and hole are localized on different atoms, and thus, following an optical excitation, the center of the electron charge is displaced, giving rise to a significant photocurrent. Janus TMDs, with their intrinsic out-of-plane asymmetry and tunable electronic properties, are particularly appealing for next-generation optoelectronic and energy-harvesting technologies. These results highlight the role of excitons in the shift-current response of Janus TMDs and demonstrate their potential as promising building blocks for future photovoltaic devices.