Quantum Oscillations and Hall Anomaly of Surface States in the Topological Insulator Bi ₂ Te ₃

TLDR

Topological insulators possess insulating bulk and massless Dirac‑like surface states with a single spin degree of freedom, yet their transport properties such as mobility remain largely unmeasured. We observed Shubnikov‑de Haas oscillations and a Hall anomaly in weak fields from the surface states of Bi₂Te₃, revealing a high surface mobility of 9,000–10,000 cm² V⁻¹ s⁻¹ and a Fermi velocity of 4 × 10⁵ m s⁻¹ that agree with ARPES measurements.

Abstract

Topological insulators are insulating materials that display massless, Dirac-like surface states in which the electrons have only one spin degree of freedom on each surface. These states have been imaged by photoemission, but little information on their transport parameters, for example, mobility, is available. We report the observation of Shubnikov-de Haas oscillations arising from the surface states in nonmetallic crystals of Bi(2)Te(3). In addition, we uncovered a Hall anomaly in weak fields, which enables the surface current to be seen directly. Both experiments yield a surface mobility (9000 to 10,000 centimeter(2) per volt-second) that is substantially higher than in the bulk. The Fermi velocity of 4 x 10(5) meters per second obtained from these transport experiments agrees with angle-resolved photoemission experiments.