Abstract
Study of the dephasing in electronic systems is not only important for probing the nature of their ground states, but also crucial to harnessing the quantum coherence for information processing. In contrast to well-studied conventional metals and semiconductors, it remains unclear which mechanism is mainly responsible for electron dephasing in three-dimensional topological insulators (TIs). Here, we report on using weak antilocalization effect to measure the dephasing rates in highly tunable (Bi,Sb)2Te3 thin films. As the transport is varied from a bulk-conducting regime to surface-dominant transport, the dephasing rate is observed to evolve from a linear temperature dependence to a sublinear power-law dependence. Although the former is consistent with the Nyquist electron-electron interactions commonly seen in ordinary 2D systems, the latter leads to enhanced electron dephasing at low temperatures and is attributed to the coupling between the surface states and the localized charge puddles in the bulk of 3D TIs.
Highlights
Study of the dephasing in electronic systems is important for probing the nature of their ground states, and crucial to harnessing the quantum coherence for information processing
Three-dimensional topological insulators (TIs) have emerged as an important class of materials that are characterized by an insulator-like bulk and gapless surface states protected by time-reversal symmetry[1,2]
We present the measurements of electron dephasing rates in 3D TI thin films with highly tunable chemical potential
Summary
Prefactor a would be equal to 1/2. In case of multi-channel WAL, the a value can vary from 1/2 to nc/2, where nc 1⁄4 2a is the number of parallel conduction channels. The nc value obtained from the HLN fit is, often far from integers due to the difference in the dephasing fields or the coherent coupling between these channels[40]. An ideal scenario is the surface-dominant transport with two symmetric channels (corresponding to a 1⁄4 1, see Supplementary Note 1) It allows for straightforward extraction of the dephasing rate with a fit to Equation (1). This transport regime, requires the bulk is insulating, and the top and bottom surfaces are decoupled and have identical dephasing fields. We propose that the coupling between the surface states and localized bulk states in a variable range hopping (VRH) regime is responsible for the enhanced electron dephasing and the sublinear temperature dependence in the surface-transport regime
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