Strong bulk photovoltaic effect in chiral crystal in the visible spectrum

TL;DR

This paper demonstrates that chiral topological insulators can exhibit a strong bulk photovoltaic effect in the visible spectrum, with shift current magnitudes significantly surpassing previous materials, opening new avenues for photovoltaic applications.

Contribution

It reveals that chiral topological trivial insulators can host large bulk photovoltaic effects and quantum CPGE, expanding the scope beyond metallic multifold fermion systems.

Findings

Photoconductivity of 20-80 uA/V2 in chiral insulators, much higher than previous materials.

Chiral insulators can host both quantum CPGE and strong shift current.

Potential platform for future photovoltaic technology development.

Abstract

Structurally chiral materials hosting multifold fermions with large topological number have attracted considerable attention because of their naturally long surface Fermi arcs and bulk quantized circular photogalvanic effect (CPGE). Multifold fermions only appear in metallic states, and therefore, most studies so far have only focused on the semimetals in compounds with chiral crystal structures. In this work, we show that the structurally chiral topological trivial insulators are also exotic states, which is interesting from the application point of view, owing to their natural advantage to host a large bulk photovoltaic effect in the visible wavelength region. In the last decades, the shift current in the visible wavelength region was limited to be 10 uA/V2 . By scanning the insulators with chiral structure, we found a class of compounds with photoconductivity ranging from 20 to 80 uA/V2 , which is approximately one order of magnitude larger than that reported in other real materials. This work illustrates that the compounds with chiral structure can host both quantum CPGE and a strong shift current in the second order optical response. Moreover, this work offers a good platform for the study of the shift current and its future application by putting the focus on insulator with chiral lattices, so far overlooked in photovoltaic technologies.