Angle-Resolved Photoemission Spectroscopy of the InsulatingNaxWO3: Anderson Localization, Polaron Formation, and Remnant Fermi Surface

Abstract

The electronic structure of the insulating sodium tungsten bronze, Na(0.025)WO(3), is investigated by high-resolution angle-resolved photoemission spectroscopy. We find that near-E(F) states are localized due to the strong disorder arising from random distribution of Na+ ions in the WO(3) lattice, which makes the system insulating. The temperature dependence of photoemission spectra provides direct evidence for polaron formation. The remnant Fermi surface of the insulator is found to be the replica of the real Fermi surface in the metallic system.

Direct evidence for hidden one-dimensional Fermi surface of hexagonalK0.25WO3

“…This weakly dispersive nature of bands is most likely due to the high background from angleintegrated spectra and disorder effect as observed in the analogous series, Na x WO 3 , where alkali-ion disorder creates a large Coulomb gap near E F . 20,21 In Fig. 3͑b͒, we plot the ARPES intensity as a function of the wave vector and the binding energy.…”

Preparation of quaternary tungsten bronze nanoparticles by a thermal decomposition of ammonium metatungstate with oleylamine

“…This results in a larger number of free electrons in the conduction band of tungsten bronze, a result that correlates well with the XPS results. The second phenomenon can be explained by the introduction of an additional localized level in the W 5+ , created by the sodium ions, which influences absorption in the range of 780-1200 nm [30]. Fig.…”

METAL-INSULATOR TRANSITION OF NaxWO3 STUDIED BY ANGLE-RESOLVED PHOTOEMISSION SPECTROSCOPY

“…In Fig. 5(d), we show the experimental valence-band structure 21,22 of Na x WO 3 for x = 0.025 and it was obtained by taking the second derivative of the ARPES spectra shown in Figs. 5(a) and 5(b).…”

“…Höchst et al 15 have performed angle-resolved photoemission spectroscopy (ARPES) on metallic Na 0.85 WO 3 single crystal with relatively low energy and momentum resolutions, and very recently we have carried out systematic high-resolution ARPES experiments on Na x WO 3 for the full range of x. [20][21][22][23] Moreover, due to the previous low energy and angular resolution of the experimental data, it was difficult to compare the experimental results with available band calculations. [24][25][26] The evolution of electronic structure with x in the metallic regime was also not clear from the previous studies.…”