"Apparent PT-symmetric terahertz photoconductivity in the topological phase of Hg1−xCdxTe-based structures"

We show that the terahertz (THz) photoconductivity in the topological phase of Hg1-xCdxTe-based structures exhibits the apparent PT- (parity-time) symmetry whereas the P-symmetry and the T-symmetry, separately, are not conserved. Moreover, it is demonstrated that the P- and T-symmetry breaking may not be related to any type of the sample anisotropy. This result contradicts the apparent symmetry arguments and means that there exists an external factor that interacts with the sample electronic system and breaks the symmetry. We show that deviations from the ideal experimental geometry may not be such a factor

Features of Energy Spectrum of Pb1−x\text{}_{1-x}Mnx\text{}_{x}Te Doped with V

Recently new effects that are not characteristic of undoped lead telluride, such as the Fermi level pinning, giant negative magnetoresistance, were observed in Pb$\text{}_{1-x}$Mn$\text{}_{x}$Te alloys doped with transition and rare earth elements - Cr, Mo, Yb. We have studied transport and magnetic properties of Pb$\text{}_{1-x}$Mn$\text{}_{x}$Te doped with another transition element - vanadium. A series of Pb$\text{}_{1-x}$Mn$\text{}_{x}$Te(V) samples of different composition and degree of doping was investigated. It was observed that the resistivity demonstrates activation behavior at low temperatures for the samples with considerable amount of vanadium as well as for the samples without vanadium. The activation energy is proportional to the Mn content. In some of the samples, photoconductivity was observed at low temperatures. The results are discussed in terms of a model assuming formation of the impurity level by the vanadium impurity and the effect of the Fermi level pinning by this level

Terahertz Photoconductivity in Hg1−x Cd x Te near the transition from the direct to inverted spectrum

For the Hg1-xCdxTe-based structures, it is shown that the transition from the direct to inverted spectrum is accompanied by the sign change for the signals related to the terahertz photoconductivity and to the magnetophotogalvanic effect. Within the range of chemical compositions corresponding to the inverted spectrum, the photoconductivity kinetics exhibits specific features, which can result from the surface topological states

Transport and Magnetic Properties of Pb1−x\text{}_{1-x}Mnx\text{}_{x}Te Doped with Cr and Mo

Transport and magnetic properties of Pb$\text{}_{1-x}$Mn$\text{}_{x}$Te (x<0.18) semiconductor alloys doped with Cr or Mo are investigated in a broad range of temperatures and magnetic fields. In PbMnTe(Cr) alloys the Fermi level may be pinned either in the conduction band or in the energy gap, depending on Mn concentration. In PbMnTe(Mo) alloys the pinning of the Fermi level is observed in the valence band as well as in the energy gap. In the latter case persistent photoconductivity is observed at low temperatures. The analysis of the temperature dependence of magnetic susceptibility shows that PbMnTe alloys doped with Cr or Mo are Curie-Weiss paramagnets revealing weak antiferromagnetic interactions between magnetic ions