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Metal-insulator transition of naxwo3 studied by angle-resolved photoemission spectroscopy

Raj, Satyabrata and Sato, Takafumi and Souma, Seigo and Takahashi, Takashi and Sarma, DD and Mahadevan, Priya (2009) Metal-insulator transition of naxwo3 studied by angle-resolved photoemission spectroscopy. In: Modern Physics Letters B (MPLB), 23 (24). pp. 2819-2846.

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Official URL: http://www.worldscinet.com/mplb/23/2324/S021798490...

Abstract

The electronic structure of sodium tungsten bronzes NaxWO3 is investigated by high-resolution angle-resolved photoemission spectroscopy (ARPES). The ARPES spectra measured in both insulating and metallic phases of NaxWO3 reveals the origin of metal-insulator transition (MIT) in sodium tungsten bronze system. It is found that in insulating NaxWO3 the states near the Fermi level (E-F) are localized due to the strong disorder caused by the random distribution of Na+ ions in WO3 lattice. Due to the presence of disorder and long-range Coulomb interaction of conduction electrons, a soft Coulomb gap arises, where the density of states vanishes exactly at E-F. In the metallic regime the states near E-F are populated and the Fermi level shifts upward rigidly with increasing electron doping (x). Volume of electron-like Fermi surface (FS) at the Gamma(X) point of the Brillouin zone gradually increases with increasing Na concentration due to W 5d t(2g) band filling. A rigid shift of the Fermi energy is found to give a qualitatively good description of the Fermi surface evolution. As we move from bulk-sensitive to more surface sensitive photon energy, we found the emergence of Fermi surfaces at X(M) and M(R) point similar to the one at the Gamma(X) point in the metallic regime, suggesting that the reconstruction of surface was due to rotation/deformation of WO6 octahedra.

Item Type: Journal Article
Additional Information: Copyright of this article belongs to World Scientific Publishing Co.,2009
Keywords: Photoemission spectroscopy; band structure; metal-insulator transition; tungsten bronze
Department/Centre: Division of Chemical Sciences > Solid State & Structural Chemistry Unit
Depositing User: Id for Latest eprints
Date Deposited: 08 Jan 2010 05:27
Last Modified: 19 Sep 2010 05:49
URI: http://eprints.iisc.ac.in/id/eprint/24212

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