Honeycomb lattice Na2IrO3 at high pressures: A robust spin-orbit Mott insulator

Authors

Xiaoxiang Xi, Nanjing University, ChinaFollow
Xiangyan Bo, Nanjing University, China
X. S. Xu, University of Nebraska-LincolnFollow
P. P. Kong, Chinese Academy of Sciences
Z. Liu, The George Washington University
X. G. Hong, Stony Brook University
C. Q. Jin, Chinese Academy of Sciences
G. Cao, University of Colorado Boulder
Xiangang Wan, Nanjing University, ChinaFollow
G. L. Carr, Brookhaven National Laboratory

Date of this Version

2018

Document Type

Article

Citation

PHYSICAL REVIEW B 98, 125117 (2018)

Comments

Used by permission.

Abstract

The honeycomb iridate Na₂IrO₃ has received much attention as a candidate to realize a quantum spin liquid state, but the nature of its insulating state remains controversial. We found that the material exhibits structural transitions at 3 and 10 GPa. The former is accompanied by 166-meV suppression of the activation gap, but the energies for the low-lying interband transitions change by less than 10 meV. This can be reconciled in a picture in which the application of high pressure barely shifts the electronic bands, but rather merely broadens them. First-principles calculations uncover a strong correlation between the band gap and the β angle of the monoclinic structure, indicating non-negligible interlayer coupling. These results offer clear evidence for a spin-orbit Mott insulating state in Na₂IrO₃ and are inconsistent with the quasimolecular orbital model.