Abstract:We report on a temperature-induced transition from a conventional semiconductor to a two-dimensional topological insulator investigated by means of magnetotransport experiments on HgTe/CdTe quantum well structures. At low temperatures, we are in the regime of the quantum spin Hall effect and observe an ambipolar quantized Hall resistance by tuning the Fermi energy through the bulk band gap. At room temperature, we find electron and hole conduction that can be described by a classical two-carrier model. Above t… Show more
“…Large positive (and often linear) MR was reported in graphene and topological insulators close to charge neutrality [14][15][16][17][18][19][20][21][22] [36][37][38][39] that this effect could be a direct condensed matter manifestation of the Adler-Bell-Jackiw chiral anomaly [40][41][42] . However, the unexpected variety of materials exhibiting negative MR [8][9][10][11][31][32][33][34][35] does not support the idea that such measurements may provide a "smoking gun" for detecting a Weyl semimetal 37,39 .…”