Observation of metallic surface states in the strongly correlated Kitaev-Heisenberg candidate Na2IrO3

Nasser Alidoust, Chang Liu, Su Yang Xu, Ilya Belopolski, Tongfei Qi, Minggang Zeng, Daniel S. Sanchez, Hao Zheng, Guang Bian, Madhab Neupane, Yu Tzu Liu, Stephen D. Wilson, Hsin Lin, Arun Bansil, Gang Cao, M. Zahid Hasan

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Abstract

We report high-resolution angle-resolved photoemission spectroscopy measurements on the honeycomb iridate Na2IrO3. Our measurements reveal the existence of a metallic surface band feature crossing the Fermi level with nearly linear dispersion and an estimated surface carrier density of 3.2×1013cm-2, which has not been theoretically predicted or experimentally observed, and provides the first evidence for metallic behavior on the boundary of this material, whereas the bulk bands exhibit a robust insulating gap. We further show the lack of theoretically predicted Dirac cones at the M points of the surface Brillouin zone, which confirms the absence of a stacked quantum spin Hall phase in this material. Our data indicates that the surface ground state of this material is exotic and metallic, unlike as predicted in theory, and establishes Na2IrO3 as a rare example of a strongly correlated spin-orbit insulator with surface metallicity.

Original languageEnglish (US)
Article number245132
JournalPhysical Review B
Volume93
Issue number24
DOIs
StatePublished - Jun 14 2016

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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    Alidoust, N., Liu, C., Xu, S. Y., Belopolski, I., Qi, T., Zeng, M., Sanchez, D. S., Zheng, H., Bian, G., Neupane, M., Liu, Y. T., Wilson, S. D., Lin, H., Bansil, A., Cao, G., & Hasan, M. Z. (2016). Observation of metallic surface states in the strongly correlated Kitaev-Heisenberg candidate Na2IrO3. Physical Review B, 93(24), [245132]. https://doi.org/10.1103/PhysRevB.93.245132