Topological insulator behavior in low-temperature electrical resistivity of the high-entropy single-crystalline thick-filmed (Bi_2/3Sb_1/3)₂ (Te_2/5Se_2/5S_1/5)₃ alloy

Abstract

High-entropy (Bi2/3Sb1/3)2(Te2/5Se2/5S1/5)3 alloy has been for the first time prepared by the self-propagating high-temperature synthesis, spark plasma sintering and melting methods. Single-crystalline and single-phased film of the alloy with thickness of ~0.11 mm was applied to find and analyze features in its electrical resistivity, which are characteristic of topological insulators. A crossover from high-temperature metal to low-temperature insulating behavior was observed in temperature dependence of the resistivity at TC≈32 K. The insulating behavior within 10÷25 K range can be due to electron-electron interaction between the 2D-electrons, existing in the surface conducting gapless states of topological insulators. Transverse magnetic field dependences of the resistivity are remarkably non-symmetric within temperature 3.5÷80 K range. The non-symmetric behavior of the magnetoresistivity is resulted from combination of antisymmetric linear and symmetric quadratic contributions. Around zero magnetic field, sharp cusps were observed within narrow magnetic field range. With increasing temperature, the cusps are gradually weaken and totally vanishing above TC. These cusps are characteristic of weak antilocalization that is one of key features of topological insulators. The cusps were analysed by in frames of the Hikami-Larkin-Nagaoka model, developed for systems with strong spin-orbit coupling. At cooling below TC, the effective dephasing length rapidly increases. Within 10÷25 K range, temperature behaviour of the dephasing length can be described by the electron-electron scattering. Below 10 K other scattering mechanisms should be also considered.