Low Energy Electrodynamics in Solids 2012

Quantum Hall effect from 2D surface states of the 3D topological insulator HgTe

23 Jul 2012, 20:00

2h

Fountain Court (Embassy Suites Napa Valley)

Board: 2

Poster Topological Insulators Poster Session 1

Speaker

Andreas V. Stier (Johns Hopkins University)

Description

Andreas V. Stier, Department of Physics and Astronomy, The Johns Hopkins University Liang Wu, Department of Physics and Astronomy, The Johns Hopkins University Christopher Morris, Department of Physics and Astronomy,The Johns Hopkins University Rolando Valdes-Aguilar,Department of Physics and Astronomy,The Johns Hopkins University Tony Almeida, US Army NVESD Alexey Suslov, National High Magnetic Field Laboratory N. Peter Armitage, Department of Physics and Astronomy, The Johns Hopkins University Three dimensional (3D) topological insulators (TI) exhibit two dimensional (2D) topologically protected conducting surface states created by strong spin-orbit coupling. Those states show a dispersion relation of massless Dirac fermions and exhibit spin-momentum locking. We present our results on high field (31T) magneto-transport experiments of the 3D topological insulator HgTe. In-plane tensile (tetragonal) strain exerted on the MBE grown 70nm thin film HgTe samples from the zinc doped CdTe substrate opens a small gap (~20 meV) and therefore lifts the band degeneracy in the center of the Brillouin zone. We study samples grown on two different crystallographic directions of the substrate material and compare the effect of varying crystallographic direction on the transport result. We observe evidence for quantized Hall (QH) resistance in both samples developing at cryogenic temperatures. We confirm the 2D character of the probed states through tilted magnetic field measurements. The observed effect is also confirmed to derive from Dirac fermions of the two TI surfaces as shown through a non-zero Berry's phase by an extrapolation of the filling factors of the QH plateaus to the large magnetic field limit. DC magneto-transport experiments are compared to zero field temperature dependent THz time domain spectroscopy data. Work at JHU was supported by the Gordon and Betty Moore foundation. A portion of this work was performed at the National High Magnetic Field Laboratory, which is supported by National Science Foundation Cooperative Agreement No. DMR-0654118, the State of Florida, and the U.S. Department of Energy.