An ab-initio study of circular photogalvanic effect in chiral multifold semimetals

TL;DR

This study uses ab-initio calculations to analyze the circular photogalvanic effect in chiral multifold semimetals, revealing that trivial bands interfere with quantization and that doping is crucial for experimental observation.

Contribution

It provides the first realistic ab-initio analysis of the quantized CPGE in chiral multifold semimetals, highlighting the importance of chemical potential tuning.

Findings

Quantized CPGE is easily interfered by trivial bands.

Doping and chemical potential tuning are essential for observing quantized CPGE.

First ab-initio study based on realistic electronic band structures.

Abstract

So far, the circular photogalvanic effect (CPGE) is the only possible quantized signal in Weyl semimetals. With inversion and mirror symmetries broken, Weyl and multifold fermions in band structures with opposite chiralities can stay at different energies and generate a net topological charge. Such kind of net topological charge can present as a quantized signal in the circular polarized light induced injection current. According to current theoretical understanding, RhSi and its counterparts are believed to be the most promising candidate for the experimental observation of the quantized CPGE. However, the real quantized signal was not experimentally observed to date. Since all the previous theoretical studies for the quantized CPGE were based on effective model but not realistic band structures, it should lose some crucial details that influence the quantized signal. The current status motives us to perform a realistic ab-initio study for the CPGE. Our result shows that the quantized value is very easy to be interfered by trivial bands related optic transitions, and an fine tuning of the chemical potential by doping is essential for the observation of quantized CPGE. This work performs the first ab-initio analysis for the quantized CPGE based on realistic electronic band structure and provides an effective way to solve the current problem for given materials.