Electronic structure and unconventional non-linear response in double Weyl semimetal SrSi$_2$

Abstract

Considering a non-centrosymmetric, non-magnetic double Weyl semimetal (WSM) SrSi2, we study the structural handedness of the material and correlate it with the distinct surface Fermi surface profile at two opposite surfaces. By investigating the electron and hole pockets in bulk Fermi surface behavior, we characterize the material as a type-I WSM. A finite energy separation between Weyl nodes of opposite chirality in SrSi2 allows us compute circular photogalvanic effect (CPGE). Followed by the three band formula, we show that CPGE is only quantized for Fermi level chosen in the vicinity of Weyl node having higher energy. Surprisingly, for the other Weyl node of opposite chirality in the lower energy, CPGE is not found to be quantized. Such a behavior of CPGE is in complete contrast to the time reversal breaking WSM where CPGE is quantized to two opposite plateau depending on the topological charge of the activated Weyl node. We further analyze our finding by examining the momentum resolved CPGE. Finally we show that two band formula for CPGE is not able to capture the quantization that is apprehended by the three band formula.