Gate-Voltage Control of Chemical Potential and Weak Antilocalization inBi2Se3

Abstract

We report that Bi₂Se₃ thin films can be epitaxially grown on SrTiO₃ substrates, which allow for very large tunablity in carrier density with a back gate. The observed low field magnetoconductivity due to weak antilocalization (WAL) has a very weak gate-voltage dependence unless the electron density is reduced to very low values. Such a transition in WAL is correlated with unusual changes in longitudinal and Hall resistivities. Our results suggest a much suppressed bulk conductivity at large negative gate voltages and a possible role of surface states in the WAL phenomena.

Coherent topological transport on the surface of Bi2Se3

“…In contrast to previous studies of WAL in TI thin films [15][16][17][18][19][20][21][22] where strong surface to bulk scattering dominates inter-channel coupling, here we report WAL measurements in gate-tuned, bulkinsulating Bi 2 Se 3 thin films where we expect negligible surfacebulk scattering. We find that the WAL behaviour in TI regime is governed by the ratio of t j to the inter-surface tunnelling time t t ¼ h/2D, where h is Planck's constant and D is the hybridization gap induced by inter-surface tunnelling 12,14 .…”

“…Therefore, a ¼ m/2 probes the number of channels m. Moreover, although crossover to WL was predicted 29 Coupling of coherent transport in Bi 2 Se 3 surface states. Figure 3 shows the variation of a obtained from the fit to equation (1) as a function of n for 17 (black), 12 (red), 7 (green) and 5 (blue) QL devices measured at 2 K. In all devices a is close to 1/2 at high nE8 Â 10 12 cm À 2 , which we interpret as WAL in a single strongly coupled coherent channel [15][16][17]19,20 in the presence of surface to bulk scattering, as bulk states becomes energetically accessible (non-TI regime). Thus, we restrict the carrier density ranging no6 Â 10 12 cm À 2 for investigating WAL behaviours in TI regime.…”

Magnetoresistance Anomaly in Topological Kondo Insulator SmB6 Nanowires with Strong Surface Magnetism

“…Many intriguing phenomena such as weak anti‐localization, quantum spin, and anomalous Hall effect have been discovered in TIs 3, 4, 5, 6. The interplay between TIs and magnetism or superconductivity can even lead to the possible realization of magnetic monopoles7 or Majorana fermions 8.…”

Transport properties of topological insulators: Band bending, bulk metal-to-insulator transition, and weak anti-localization

“…In thin-film samples of Bi 2 Se 3 à is not the ideal value of 2, but rather close to half of this at à ≈ 1 [27,[44][45][46][47][48]] (see Fig. 7).…”