Photoelectromagnetic Effect Induced by Terahertz Laser Radiation in Topological Crystalline Insulators Pbl-xSnx Te

We studied the photoelectromagnetic (PEM) effect induced by laser terahertz radiation in $\text{Pb}_{1_{-x}}\text{Sn}_{x}\text{Te}$ films in the composition range $x=(0.15-0.45)$. A transition from the trivial phase to the topological crystalline insulator phase occurs within this composition interval at $x=0.35$. The films had the crystallographic orientation $< 111 >$, for which the appearance of topologically nontrivial surface states is expected. It was found that in the trivial phase, the amplitude of the PEM effect is determined by the power of the incident radiation, while in the topological phase, the amplitude is proportional to the flux of laser radiation quanta. Possible mechanism leading to the observed effect is discussed.