Enhanced Mobility of Spin-Helical Dirac Fermions in Disordered 3D Topological Insulators.
basic_science · Level V
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Abstract
The transport length l<sub>tr</sub> and the mean free path l<sub>e</sub> are determined for bulk and surface states in a Bi<sub>2</sub>Se<sub>3</sub> nanoribbon by quantum transport and transconductance measurements. We show that the anisotropic scattering of spin-helical Dirac fermions results in a strong enhancement of l<sub>tr</sub> (≈ 200 nm) and of the related mobility μ<sub>tr</sub> (≈ 4000 cm<sup>2</sup> V<sup>-1</sup> s<sup>-1</sup>), which confirms theoretical predictions.1 Despite strong disorder, the long-range nature of the scattering potential gives a large ratio l<sub>tr</sub>/l<sub>e</sub> ≈ 8, likely limited by bulk/surface coupling. This suggests that the spin-flip length l<sub>sf</sub> ≈ l<sub>tr</sub> could reach the micron size in materials with a reduced bulk doping and paves the way for building functionalized spintronic and ballistic electronic devices out of disordered 3D topological insulators.