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arXiv · 1309.2945

Polarity-driven surface metallicity in SmB$_6$

Z. -H. Zhu·A. Nicolaou·G. Levy·N. P. Butch·P. Syers·X. F. Wang·J. Paglione·G. A. Sawatzky·I. S. Elfimov·A. Damascelli
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Abstract

By a combined angle-resolved photoemission spectroscopy and density functional theory study, we discover that the surface metallicity is polarity-driven in SmB$_6$. Two surface states, not accounted for by the bulk band structure, are reproduced by slab calculations for coexisting B$_6$ and Sm surface terminations. Our analysis reveals that a metallic surface state stems from an unusual property, generic to the (001) termination of all hexaborides: the presence of boron $2p$ dangling bonds, on a polar surface. The discovery of polarity-driven surface metallicity sheds new light on the 40-year old conundrum of the low-temperature residual conductivity of SmB$_6$, and raises a fundamental question in the field of topological Kondo insulators regarding the interplay between polarity and nontrivial topological properties.

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Z. -H. Zhu, A. Nicolaou, G. Levy, N. P. Butch, P. Syers, X. F. Wang, J. Paglione, G. A. Sawatzky, I. S. Elfimov, A. Damascelli. 2013-11-20. Polarity-driven surface metallicity in SmB$_6$. https://doi.org/10.1103/physrevlett.111.216402

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