Electronic structure of sodium tungsten bronzes NaxWO3 by high-resolution angle-resolved photoemission spectroscopy

Raj, S. ; Matsui, H. ; Souma, S. ; Sato, T. ; Takahashi, T. ; Chakraborty, A. ; Sarma, D. D. ; Mahadevan, P. ; Oishi, S. ; McCarroll, W. H. ; Greenblatt, M. (2007) Electronic structure of sodium tungsten bronzes NaxWO3 by high-resolution angle-resolved photoemission spectroscopy Physical Review B: Condensed Matter and Materials Physics, 75 (15). 155116_1-155116_11. ISSN 1098-0121

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Official URL: http://prb.aps.org/abstract/PRB/v75/i15/e155116

Related URL: http://dx.doi.org/10.1103/PhysRevB.75.155116

Abstract

The electronic structure of sodium tungsten bronzes, NaxWO3, for full range of x is investigated by high-resolution angle-resolved photoemission spectroscopy (HR-ARPES). The experimentally determined valence-band structure has been compared with the results of ab initio band-structure calculation. The HR-ARPES spectra taken in both the insulating and metallic phase of NaxWO3 reveal the origin of metal-insulator transition (MIT) in the sodium tungsten bronze system. In the insulating NaxWO3, the near-EF states are localized due to the strong disorder caused by the random distribution of Na+ ions in WO3 lattice. While the presence of an impurity band (level) induced by Na doping is often invoked to explain the insulating state found at low concentrations, there is no signature of impurity band (level) found from our results. Due to disorder and Anderson localization effect, there is a long-range Coulomb interaction of conduction electrons; as a result, the system is insulating. In the metallic regime, the states near EF are populated and the Fermi level shifts upward rigidly with increasing electron doping (x). The volume of electronlike Fermi surface (FS) at the Γ(X) point gradually increases with increasing Na concentration due to W 5dt2g band filling. A rigid shift of EF is found to give a qualitatively good description of the FS evolution.

Item Type:Article
Source:Copyright of this article belongs to The American Physical Society.
ID Code:46411
Deposited On:04 Jul 2011 12:09
Last Modified:18 May 2016 02:18

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