Ultrafast shift current dynamics in WS$_{2}$ monolayer

TL;DR

This study uses real-time TDDFT to investigate ultrafast shift current dynamics in monolayer WS2, revealing rapid generation and dissipation within tens of femtoseconds, advancing understanding for ultrafast photodetectors.

Contribution

It provides the first real-time simulation of shift current dynamics in WS2 monolayer, highlighting ultrafast response times crucial for device applications.

Findings

Shift current generated within 10-20 fs after illumination

Dissipates within a few tens of femtoseconds after light is off

Potential for ultrafast photon detection

Abstract

The shift current effect, in materials lacking inversion symmetry, may potentially allow the performance of photovoltaics to surpass the Shockley-Queisser limit for traditional p-n junction-based photovoltaics. Although the shift-current effect has been studied from first-principles via second-order perturbation theory, an understanding of the dynamics of hot carriers is still lacking. We investigate the dynamics of the shift current in monolayer WS$_{2}$ via real-time propagation time-dependent density functional theory (rt-TDDFT). We find that the shift current can be generated within 10 - 20 fs after turning on the lights and dissipates within approximately a few tens of femtoseconds after turning off the lights. This property can be used for ultrafast photon detection. This work provides an important step toward understanding the dynamics of shift-current effects, which is crucial for device applications.