Berlin 2015 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 24: Transport II: Thermal and Electrical Conductivity
MM 24.3: Vortrag
Dienstag, 17. März 2015, 12:15–12:30, H 0107
Topological insulators defined by local and non-local resistivity — •C. Shekhar1, S. Ouardi1, C. E. ViolBarbosa1, B. Yan1,2, W. Schnelle1, G. H. Fecher1, and C. Felser1 — 1Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany — 2Max Planck Institute for Physics of the Complex Systems, 01187 Dresden, Germany
Topological insulators are known for their metallic surface states, a result of strong spin-orbit coupling, that exhibit unique surface transport phenomenon. However, these surface transport phenomena are buried in the presence of metallic bulk conduction. We synthesized very high quality Bi_2 Te_2 Se single crystals by using a modified Bridgman method that possess high bulk resistivity of >20 Omega cm below 20K, whereas the bulk is mostly inactive and surface transport dominates. The temperature dependence of resistivity follows an activation law like a gap semiconductor in temperature range 20-300K. To define the topological property i.e. extract the surface transport from that of the bulk, we designed a special measurement geometry to measure the resistance in local and non-local regions. We find that single-crystal Bi_2 Te_2 Se exhibits a crossover from bulk to surface conduction at 20K. Simultaneously, the material also shows strong evidence of surface transport in magneto-conductance. This novel simple geometry facilitates finding evidence of surface transport in topological insulators, which are promising materials for future spintronic applications.