Disorder Effects in the Bipolaron System Ti${}_4$O${}_7$ Studied by Photoemission Spectroscopy

Abstract

We have performed a photoemission study of Ti${}_4$O${}_7$ around its two transition temperatures so as to cover the metallic, high-temperature insulating (bipolaron-liquid), and low-temperature insulating (bipolaron-crystal) phases. While the spectra of the low-temperature insulating phase show a finite gap at the Fermi level, the spectra of the high-temperature insulating phase are gapless, which is interpreted as a soft Coulomb gap due to dynamical disorder. We suggest that the spectra of the high-temperature disordered phase of Fe${}_3$O${}_4$, which exhibits a charge order-disorder transition (Verwey transition), can be interpreted in terms of a Coulomb gap.

4 pages, 3 epsf figures embedded

References in corpus (1)

• The Density of States of hole-doped Manganites: A Scanning Tunneling Microscopy/Spectroscopy study

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