Two-dimensional Fermi surfaces in Kondo insulator SmB6

Science  05 Dec 2014:
Vol. 346, Issue 6214, pp. 1208-1212
DOI: 10.1126/science.1250366

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In the Kondo insulator samarium hexaboride (SmB6), strong correlation and band hybridization lead to an insulating gap and a diverging resistance at low temperature. The resistance divergence ends at about 3 kelvin, a behavior that may arise from surface conductance. We used torque magnetometry to resolve the Fermi surface topology in this material. The observed oscillation patterns reveal two Fermi surfaces on the (100) surface plane and one Fermi surface on the (101) surface plane. The measured Fermi surface cross sections scale as the inverse cosine function of the magnetic field tilt angles, which demonstrates the two-dimensional nature of the conducting electronic states of SmB6.

Teasing out the topological character

When theoretical physicists proposed the existence of an exciting class of materials called topological insulators (TIs), they had in mind a material that is electrically insulating in the bulk but conducts electricity on its surface. Experimentally discovered TIs, however, still have considerable bulk conductivity. Theoreticians then noticed that the material SmB6, which has long been known as an insulator with peculiar conduction properties, may be a TI. However, confirming that SmB6 is a TI has been an arduous process. Li et al. traced the electronic structure of SmB6 in high magnetic fields and found that it does indeed have two-dimensional surface states.

Science, this issue p. 1208

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