Thermoreflectometry of single crystals of mercury selenide in the range of 35–300 K in a fiber-optic “pump-probe” scheme with a Fabry–Perot interferometer

A study of the reflection of infrared radiation at a wavelength of $1530$ nm from the surface of HgSe single crystals in a two-beam pump-probe fiber-optic scheme was carried out using the thermoreflectometry (TR) method with a Fabry–Perot interferometer (FP). Along with the “high-temperature” anomaly of the probe laser signal (at $T>100$ K) in the relaxation region, a “low-temperature” anomaly was revealed in the heating region, consisting in a change in signal polarity at $T<50$ K. A qualitative interpretation of the observed features of the relative intensity of the reflected signal in the region of heating and relaxation is proposed, based on the hypothesis of two types of energy barriers, separating the bulk chiral states from the Fermi-arc surface states.