Enhancing the circular photogalvanic effect in double Weyl semimetals via symmetry breaking

Weyl semimetals have emerged as a hot topic in condensed matter physics in last decade. Beyond their intriguing electrical transport phenomena, such as the negative magnetoresistance driven by the chiral anomaly and the anomalous Hall effect, they also exhibit intriguing second-order optoelectronic responses, such as the circular photogalvanic effect (CPGE). In this Letter, we investigate the CPGE in a class of double Weyl semimetal protected by the C3zT symmetry by using the effective model. Unlike double Weyl semimetal protected by Cnz (n = 4, 6) symmetry, when time-reversal symmetry T is broken, one C3zT-protected double Weyl point (WP) evolves into four single WPs, three of which are related by C3z symmetry, and these WPs share the same topological charge and reside at the same energy level. This unique configuration enhances the CPGE trace due to the combined topological charge of the three WPs, resulting in a higher quantized plateau. Our findings provide promising prospects for the development of optoelectronic devices in the future.