Na2IrO3 as a novel relativistic Mott insulator with a 340-meV gap.
We study Na2IrO3 by angle-resolved photoemission spectroscopy, optics, and band structure calculations in the local-density approximation (LDA). The weak dispersion of the Ir 5d-t(2g) manifold highlights the importance of structural distortions and spin-orbit (SO) coupling in driving the system closer to a Mott transition. We detect an insulating gap Δ(gap)≃340  meV which, at variance with a Slater-type description, is already open at 300 K and does not show significant temperature dependence even across T(N)≃15  K. An LDA analysis with the inclusion of SO and Coulomb repulsion U reveals that, while the prodromes of an underlying insulating state are already found in LDA+SO, the correct gap magnitude can only be reproduced by LDA+SO+U, with U=3  eV. This establishes Na2IrO3 as a novel type of Mott-like correlated insulator in which Coulomb and relativistic effects have to be treated on an equal footing.
Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada.
R
R
Comin
G
G
Levy
B
B
Ludbrook
Z-H
ZH
Zhu
C N
CN
Veenstra
J A
JA
Rosen
Yogesh
Y
Singh
P
P
Gegenwart
D
D
Stricker
J N
JN
Hancock
D
D
van der Marel
I S
IS
Elfimov
A
A
Damascelli