Nonlocal Chemical Potential Modulation in Topological Insulators Enabled by Highly Mobile Trapped Charges

Topological insulators (TIs) host unusual surface states with Dirac dispersion and helical spin texture and hold high potential for applications in spintronics and quantum computing. However, unintentional doping due to native defects in these materials creates a key obstacle to displaying their desired unique spin and charge transport properties. Here, we report a simple and effective method that can in situ tune the chemical potential in Bi2–xSbxSe3 nanoribbon devices, with a magnitude significantly larger than traditional electrostatic gating. An electric field parallel to a device channel alters the chemical potential both in the channel and out of the channel. We demonstrate that such modulation is enabled by fast charge diffusion among defect states, further visualized by photocurrent mapping. Our observations enable dynamic chemical potential engineering, providing tremendous opportunities for investigating fundamental transport mechanisms of charge and composite particles, such as excitons, in TIs.