Skip to main content
eScholarship
Open Access Publications from the University of California

UCLA

UCLA Electronic Theses and Dissertations bannerUCLA

Enhancement of Topological Insulators Surface Conduction

Abstract

The quantum spin Hall (QSH) phase exhibits spontaneous quantized (charge/spin) conductance in the absence of external magnetic field, as a result of strong spin-orbit coupling. However, due to the large bulk contribution in 3D TIs, it is difficult to observe these new states. Here we first demonstrate a selective control of two surfaces conductions (top/bottom) in epitaxially grown Bi2Te3 thin films by gate-dependent Shubnikov-de Hass oscillations. By sweeping the gate voltage, the Fermi level of the top surface is selectively tuned while the bottom surface conduction remains unchanged due to strong electric-field screening effects arising from the high dielectric constant of Bi2Te3. In addition, the total bulk conduction can be modulated from n- to p-type with a varying gate bias. We further investigate BixSb2-xTe3 as it provides lower bulk contribution and enhanced two surface conductions. These Sb-doped materials provide us a good opportunity to see the quantum spin Hall result.

Main Content
For improved accessibility of PDF content, download the file to your device.
Current View