Coherent transport in density-tunable topological surface states in Bi2Se3

TYPECondensed Matter Seminar
Speaker:Hadar Steinberg
Location:Lidow Nathan Rosen (300)

I will present our studies of electronic transport in the density-tunable surface states of the Topological Insulator (TI) Bi2Se3. TI surface states, intensively studied by ARPES and STM, pose a challenge for transport experiments due to parallel conduction through bulk states, limited surface density tunability, and uncertainty in the surface-to-bulk coupling. To single out the surface transport we study thin devices (<100 nm) fabricated by two different approaches: (i) Bi2Se3 flakes exfoliated from single crystals1; (ii) Devices patterned from evaporated thin films. In the thin film devices transport is dominated by the surface states, and exhibits pronounced ambipolar resistance modulation2.

The TI devices exhibit an unusual weak-antilocalization correction to conductance, which appears to be carried by multiple coherently-independent channels. The effective number of independent channels depends on the voltage of the density-tuning gate, on temperature, and on the bulk doping. We suggest that this is a consequence of tunable surface-to-bulk coupling, and that our results provide an indication that the surface state individually exhibits the weak-antilocalization correction, as expected from its chiral properties.


1. Surface State Transport and Ambipolar Electric Field Effect in Bi2Se3 Nanodevices. H. Steinberg, D. Gardner, Y. Lee & P. Jarillo-Herrero. Nano Letters 10, 5032-5036 (2010).

2. Electrically tunable surface-to-bulk coherent coupling in topological insulator thin films. H. Steinberg, J.-B. Laloë, V. Fatemi, J.-S. Moodera & P. Jarillo-Herrero. arXiv:1104.1404 (2011).