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Disorder Effects in the Bipolaron System Ti$_{4}$O$_{7}$ Studied by Photoemission Spectroscopy

K. Kobayashi·T. Susaki·A. Fujimori·T. Tonogai·H. Takagi
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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.

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K. Kobayashi, T. Susaki, A. Fujimori, T. Tonogai, H. Takagi. 1999-09-13. Disorder Effects in the Bipolaron System Ti$_{4}$O$_{7}$ Studied by Photoemission Spectroscopy. https://doi.org/10.1209/epl%2Fi2002-00123-2

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