# Large terahertz photovoltaic effect enhanced by phonon excitations in ferroelectric semiconductor SbSI

## TL;DR

This paper shows how terahertz light can generate large electric currents in a material called SbSI by exciting vibrations in its structure.

## Contribution

The study reveals that terahertz photocurrent in SbSI is enhanced by phonon excitations, offering a new pathway for efficient terahertz technology.

## Key findings

- Terahertz photocurrent in SbSI is resonantly enhanced by optical phonons.
- Phonon-driven shift current efficiency rivals that of electronic shift current in TaAs.
- Theoretical models and calculations support the observed terahertz shift current behavior.

## Abstract

Quantum geometry of Bloch electron in crystalline solids produces various exotic quantum phenomena. The shift current photovoltaic effect driven by the photo creation of quasiparticle is one such emerging example that enables the conversion from terahertz photon into dc charge current with absence of dissipative photocarrier. Despite wide-ranging potential applications, however, the fundamental nature of terahertz photovoltaic response has remained elusive. Here, we show the large photocurrent generation driven by terahertz phonons (<10 milli–electron volts) in ferroelectric semiconductor SbSI with the electronic bandgap of 2.3 electron volts. Zero-bias terahertz photocurrent is found to be resonantly enhanced by optical phonons. Its generation efficiency is larger than that for the direct interband transition and is comparable to the electronic shift current in Weyl semimetal TaAs. The theoretical scaling law of terahertz shift current and first-principles calculation reasonably explain these observations. The present work establishes the universality and high efficiency of phonon-driven shift current, opening the pathway to terahertz technology based on quantum geometry.

Quantum geometry of matter enables gigantic terahertz shift current generation through photo-creation of optical phonons.