Discrimination of Conductive Surface Electron States by Laser Terahertz Radiation in PbSe—A Base for Pb$_{1-x}$Sn$_x$Se Topological Crystalline Insulators

We report on the influence of oxidation on features of surface electron states in PbSe films-materials belonging to the family of topological crystalline insulators Pb
_1-x
Sn
_x
Se. These states are detected through observation of the photoelectromagnetic effect induced by terahertz laser pulses. It is demonstrated that highly conductive surface electron states in PbSe are inherent to the semiconductor itself and are not related to the material oxidation. This allows excluding surface states induced by oxidation as a reason for high surface conductivity in topological crystalline insulators based on Pb
_1-x
Sn
_x
Se.