Observation of Metallic Surface States in the Strongly Correlated Kitaev-Heisenberg Candidate Na₂IrO₃

Authors

Nasser Alidoust, Princeton University
Chang Liu, Princeton University
Su-Yang Xu, Princeton University
Ilya Belopolski, Princeton University
Tongfei Qi, University of KentuckyFollow
Minggang Zeng, National University of Singapore, Singapore
Daniel S. Sanchez, Princeton University
Hao Zheng, Princeton University
Guang Bian, Princeton University
Madhab Neupane, Princeton University
Yu-Tzu Liu, National University of Singapore, Singapore
Stephen D. Wilson, University of California - Santa Barbara
Hsin Lin, National University of Singapore, Singapore
Arun Bansil, Northeastern University
Gang Cao, University of KentuckyFollow
M. Zahid Hasan, Princeton University

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 x 10¹³ cm^-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.

Document Type

Article

Publication Date

6-14-2016

Notes/Citation Information

Published in Physical Review B, v. 93, issue 24, 245132, p. 1-6.

©2016 American Physical Society

The copyright holder has granted permission for posting the article here.

Digital Object Identifier (DOI)

https://doi.org/10.1103/PhysRevB.93.245132

Funding Information

Work at Princeton University is supported by the US National Science Foundation Grant No. NSF-DMR-1006492. M.Z.H. acknowledges visiting scientist support from Lawrence Berkeley National Laboratory and additional partial support from the A. P. Sloan Foundation and NSF-DMR-0819860. G.C. acknowledges NSF support via Grant No. DMR 1265162. The photoemission measurements using synchrotron x-ray facilities are supported by the Basic Energy Sciences of the US Department of Energy under DE-FG-02-05ER46200.

Related Content

See Supplemental Material at http://link.aps.org/supplemental/10.1103/PhysRevB.93.245132 for analysis of the low-energy electron diffraction data, comparison to the bulk energy distribution curves previously reported, Lorentzians used to fit to the momentum distribution curves of the metallic in-gap states, and the linear fits to the peak positions of these Lorentzians.

Repository Citation

Alidoust, Nasser; Liu, Chang; Xu, Su-Yang; Belopolski, Ilya; Qi, Tongfei; Zeng, Minggang; Sanchez, Daniel S.; Zheng, Hao; Bian, Guang; Neupane, Madhab; Liu, Yu-Tzu; Wilson, Stephen D.; Lin, Hsin; Bansil, Arun; Cao, Gang; and Hasan, M. Zahid, "Observation of Metallic Surface States in the Strongly Correlated Kitaev-Heisenberg Candidate Na₂IrO₃" (2016). Center for Advanced Materials Faculty Publications. 6.
https://uknowledge.uky.edu/cam_facpub/6