Surface-bulk coupling in a Bi\(_2\)Te\(_3\) nanoplate grown by van der Waals epitaxy

• Published in: arXiv.org 2022-02
• Main Authors: Li, Xiaobo, Meng, Mengmeng, Huang, Shaoyun, Tan, Congwei, Zhang, Congcong, Peng, Hailin, Xu, H Q
• Format: Article
• Language: English
• Subjects: Carrier density; Coherent scattering; Conductivity; Coupling; Electric potential; Electrons; Epitaxial growth; Low temperature; Magnetic fields; Mica; Quantum transport; Substrates; Topological insulators; Voltage
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2202.05004

We report on an experimental study of the effect of coherent surface-bulk electron scattering on quantum transport in a three-dimensional topological insulator Bi\(_2\)Te\(_3\) nanoplate. The nanoplate is grown via van der Waals epitaxy on a mica substrate and a top-gated Hall-bar device is fabricated from the nanoplate directly on the growth substrate. Top-gate voltage dependent measurements of the sheet resistance of the device reveal that the transport carriers in the nanoplate are of n-type and that, with decreasing top gate voltage, the carrier density in the nanoplate is decreased. However, the mobility is increased with decreasing top-gate voltage. This mobility increase with decreasing carrier density in the nanoplate is demonstrated to arise from a decrease in bulk-to-surface electron scattering rate. Low-field magnetotransport measurements are performed at low temperatures. The measured magnetoconductivity of the nanoplate shows typical weak anti-localization (WAL) characteristics. We analyze the measurements by taking surface-bulk inter-channel electron scattering into account and extract dephasing times \({\tau}_{\phi}\), diffusion coefficients \(D\) of electrons at the top surface and in the bulk, and the surface-bulk scattering times \({\tau}_{SB}\) as a function of top-gate voltage and temperature. It is found that the dephasing in the nanoplate arises dominantly from electron-electron scattering with small energy transfers. It is also found that the ratio of \({\tau}_{\phi}\)/\({\tau}_{SB}\) (a measure of the surface-bulk electron coherent coupling) is decreased with decreasing gate voltage or increasing temperature. We demonstrate that taking the surface-bulk coherent electron scattering in our Bi\(_2\)Te\(_3\) nanoplate into account is essential to understand quantum transport measurements at low temperatures.