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Phys Rev Lett. 2015 Mar 6;114(9):096601. Epub 2015 Mar 3.

Tuning bulk and surface conduction in the proposed topological Kondo insulator SmB(6).

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Center for Nanophysics and Advanced Materials, Department of Physics, University of Maryland, College Park, Maryland 20742, USA.
Department of Physics, University of Wisconsin, Madison, Wisconsin 53706, USA.
School of Physics, Monash University, Melbourne, Victoria 3800, Australia.
Canadian Institute for Advanced Research, Toronto, Canada M5G 1Z8.


Bulk and surface state contributions to the electrical resistance of single-crystal samples of the topological Kondo-insulator compound SmB_{6} 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 (100) 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, exhibits a field-effect mobility of 133  cm^{2}/Vs and a large carrier density of ∼2×10^{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.

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