Tuning bulk and surface conduction in topological Kondo insulator SmB6

TL;DR

This study investigates how bulk and surface conduction in the topological Kondo insulator SmB6 can be independently tuned using crystal thickness and ionic liquid gating, revealing a model with an insulating bulk and metallic surface states.

Contribution

It demonstrates a method to separately control bulk and surface conduction in SmB6, providing conclusive evidence for the bulk-insulating, surface-metallic model and showing gate-tunable surface conductance.

Findings

Surface conductance of ~100 e^2/h with electron-like carriers

Field-effect mobility of 133 cm^2/V/s

Surface conduction modulated by more than 25%

Abstract

Bulk and surface state contributions to the electrical resistance of single-crystal samples of the topological Kondo insulator compound SmB6 are investigated as a function of crystal thickness and surface charge density, the latter tuned by ionic liquid gating with electrodes patterned in a Corbino disk geometry on a single surface. By separately tuning bulk and surface conduction channels, we show conclusive evidence for a model with an insulating bulk and metallic surface states, with a crossover temperature that depends solely on the relative contributions of each conduction channel. The surface conductance, on the order of 100 e^2/h and electron-like, exhibits a field-effect mobility of 133 cm^2/V/s and a large carrier density of ~2x10^{14}/cm^2, in good agreement with recent photoemission results. With the ability to gate-modulate surface conduction by more than 25%, this approach provides promise for both fundamental and applied studies of gate-tuned devices structured on bulk crystal samples.