Terahertz probing of surface electron states in topological crystalline insulators Pb1−xSnxSe

We suggest a method for detection of highly conductive surface electron states including topological ones. The method is based on measurements of the photoelectromagnetic effect using terahertz laser pulses. In contrast to conventional transport measurements, the method is not sensitive to the bulk conductivity. The method is demonstrated on an example of topological crystalline insulators Pb_1-xSn_xSe. It is shown that highly conductive surface electron states are present in Pb_1-xSn_xSe both in the inverse and direct electron energy spectrum.