Polarity-driven surface metallicity in SmB${}_6$

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.

5 pages, 4 figures. A high-resolution version with supplementary material can be found at: http://www.phas.ubc.ca/~quantmat/ARPES/PUBLICATIONS/Articles/SmB6

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• Correlated Topological Insulators with Mixed Valence
• Surface and Bulk Electronic Structure of the Strongly Correlated System SmB${}_6$ and Implications for a Topological Kondo Insulator
• Hybridization, Inter-Ion Correlation, and Surface States in the Kondo Insulator SmB6
• Determining the Surface-To-Bulk Progression in the Normal-State Electronic Structure of Sr2RuO4 by Angle-Resolved Photoemission and Density Functional Theory

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