Topological Optical Pseudospin Injection Beyond Weyl Semimetals

Photoinduced effects are now reckoned to be important tools to reveal a rich gamut of entrancing physics in topological materials, which are normally inaccessible to conventional probes. Here we investigate one of these intriguing effects, namely, optical pseudospin injection (OPI) beyond ordinary Weyl semimetals (WSMs), specifically in multi-WSMs (mWSMs) and higher-order WSMs. Remarkably, we demonstrate that OPI in mWSMs is independent of the frequency of the light and linearly proportional to the quantized topological charge as a consequence of the inherent band linearity in their dispersions. Interestingly, while the response does not depend on the tilting of a type-I node, it is a decreasing function of the same in type-II mWSMs. We also reveal that the frequency independence can be destroyed either by going beyond a certain cutoff frequency under lattice regularization or by going to a higher-order Weyl phase. The predicted signatures of OPI beyond the ordinary WSM could be experimentally exploited, leading to effective access as well as distinguishing between different nontrivial Weyl topologies.