Phase transition and anomalous scaling in the quantum Hall transport of topological-insulator Sn-Bi_1.1Sb_0.9Te₂S devices

The scaling physics of quantum Hall transport in optimized topological insulators with a plateau precision of ∼1/1000 e²/h is considered. Two exponential scaling regimes are observed in temperature-dependent transport dissipation, one of which accords with thermal-activation behavior with a gap of 2.8 meV (>20 K), the other being attributed to variable-range hopping (1–20 K). Magnetic-field-driven plateau-to-plateau transition gives scaling relations of (dR_xy/dB)^max ∝ T ^−κ and △B⁻¹ ∝ T ^−κ with a onsistent exponent of κ ∼ 0.2, which is half the universal value for a conventional two-dimensional electron gas. This is evidence of percolation assisted by quantum tunneling and reveals the dominance of electron-electron interaction of the topological surface states.