Se topological quantum wells*

Pb_1-xSn_xSe(0.16<x<0.4) is a semiconductor with narrow band gap and can transit from trivial to topological crystalline insulator (TCI) as Sn concentration increases. It is a valley degenerate system with strong spin-orbit coupling, providing a platform to study exotic quantum Hall phenomenon. However, such effect can only be achieved on high quality quantum wells, which have not been well studied yet. Here we investigated the MBE growth of Pb_0.92Eu_0.08Te/Pb_0.7Sn_0.3Se/ Pb_0.92Eu_0.08Te quantum well and characterized the sample by XRD, TEM and magneto-transport measurement. We were able to make single wells with low carrier density and high mobility(>10000cm²/Vs). By properly doping with Bi and gating, Shubnikov-de Haas oscillation were observed. A 2-D density and effective mass are calculated from the oscillation correlate well with Hall measurements. The oscillations also agree with what is expected for the Landau levels extracted from a k.p quantum well model allows us to estimate that B=20T is required to reach the quantum limit. Our work has achieves needed progress for future studies of the unconventional Hall-quantized regime of in the quantum limit of TCIs.