Li Xiaobo, Meng Mengmeng, Huang Shaoyun, Tan Congwei, Zhang Congcong, Peng Hailin, Xu H Q
Beijing Key Laboratory of Quantum Devices, Key Laboratory for the Physics and Chemistry of Nanodevices, and School of Electronics, Peking University, Beijing 100871, China.
Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871, China.
Nanoscale. 2022 Feb 17;14(7):2586-2592. doi: 10.1039/d1nr08054g.
We report an experimental study of the effect of coherent surface-bulk electron scattering on quantum transport in a three-dimensional topological insulator BiTe nanoplate. The nanoplate is grown 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 , diffusion coefficients of electrons at the top surface and in the bulk, and the surface-bulk scattering times 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 / (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 BiTe nanoplate into account is essential to understand quantum transport measurements at low temperatures.
我们报告了一项关于相干表面 - 体电子散射对三维拓扑绝缘体BiTe纳米板中量子输运影响的实验研究。该纳米板通过范德华外延生长在云母衬底上，并直接在生长衬底上由该纳米板制备了顶栅霍尔条形器件。对该器件的薄层电阻进行的与顶栅电压相关的测量表明，纳米板中的输运载流子为n型，并且随着顶栅电压的降低，纳米板中的载流子密度降低。然而，迁移率随着顶栅电压的降低而增加。纳米板中迁移率随载流子密度降低而增加被证明是由于体到表面电子散射率的降低。在低温下进行了低场磁输运测量。纳米板的测量磁导率显示出典型的弱反局域化（WAL）特性。我们通过考虑表面 - 体通道间电子散射来分析测量结果，并提取退相时间、顶表面和体中的电子扩散系数以及作为顶栅电压和温度函数的表面 - 体散射时间。发现纳米板中的退相主要源于小能量转移的电子 - 电子散射。还发现 / （表面 - 体电子相干耦合的一种度量）的比值随着栅极电压降低或温度升高而降低。我们证明，考虑我们的BiTe纳米板中的表面 - 体相干电子散射对于理解低温下的量子输运测量至关重要。
