ИСТИНА

: Topological insulator represents an unconventional quantum phase of matter with insulating bulk band gap and metallic surface states. Recent theoretical prediction and photoemission spectroscopy measurements show that group V-VI materials Bi2Se3, Bi2Te3, Sb2Te3 and more complicate compounds as Bi2Te2Se are TIs with a single Dirac cone due to the surface states. These materials have anisotropic, layered structures, in which five atomic layers are covalently bonded to form a quintuple layer, and quintuple layers interact weakly through van der Waals interaction to form the crystal. A few quintuple layers of these materials are predicted to exhibit interesting surface properties. Here we report the synthesis and characterizations of ultrathin Bi2Te2Se nanoplates with thickness down to a few nm (a few quintuple layers) and lateral dimension is about (300-100) nm, via catalyst-free vapor-solid growth mechanism [1-3]. As a new member of TI nanomaterials, ultrathin TI nanoplates have an extremely large surface-to-volume ratio and can be electrically gated more effectively than the bulkform, potentially enhancing surface state effects in transport measurements. Low-temperature transport measurements of a single nanoplate device, demonstrate the superconducting proximity effect in nanoplate of topological insulator (Bi2Te2Se) which is interfaced with superconducting (niobium) contacts. On dI/dV curves we observe the effects which can be linked with a multiple Andreev reflections for channel lengths that are much longer than the inelastic and diffusive thermal lengths deduced from normal state transport. Authors acknowledge the Russian Foundation for Basic Research (RFBR) (research projects No. 16-02-00727, 16-32-60133 and No. 16-02-00815). [1] Yan, Y.et al. Synthesis and Quantum Transport Properties of Bi2Se3 45 Topological Insulator Nanostructures. Sci. Rep. 3, 1264; DOI:10.1038/srep01264 (2013). [2] Schönherr et al.: Vapour-liquid-solid growth of ternary Bi2Se2Te nanowires. Nanoscale Research Letters 2014 9:127. [3] Kong, D.; Randel, J. C.; Peng, H.; Cha, J. J.; Meister, S.; Lai, K.; Chen, Y.; Shen, Z.- X.; Manoharan, H. C.; Cui, Y. Nano Lett. t. 2010, 10, 2245—2250. Acoustic resonator for superconducting qu