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Evolution of the electronic structure from electron-doped to hole-doped states in the two-dimensional Mott-Hubbard system La1.17-xPbxVS3.17

A. Ino·T. Okane·S. -I. Fujimori·A. Fujimori·T. Mizokawa·Y. Yasui·T. Nishikawa·M. Sato
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Abstract

The filling-controlled metal-insulator transition (MIT) in a two-dimensional Mott-Hubbard system La1.17-xPbxVS3.17 has been studied by photoemission spectroscopy. With Pb substitution x, chemical potential mu abruptly jumps by ~ 0.07 eV between x=0.15 and 0.17, indicating that a charge gap is opened at x ~= 0.16 in agreement with the Mott insulating state of the d2 configuration. When holes or electrons are doped into the Mott insulator of x ~= 0.16, the gap is filled and the photoemission spectral weight at mu, rho(mu), gradually increases in a similar way to the electronic specific heat coefficient, although the spectral weight remains depressed around mu compared to that expected for a normal metal, showing a pseudogap behavior in the metallic samples. The observed behavior of varrho(mu)->0 for x->0.16 is contrasted with the usual picture that the electron effective mass of the Fermi-liquid system is enhanced towards the metal-insulator boundary. With increasing temperature, the gap or the pseudogap is rapidly filled up, and the spectra at T=300 K appears to be almost those of a normal metal. Near the metal-insulator boundary, the spectra around mu are consistent with the formation of a Coulomb gap, suggesting the influence of long-range Coulomb interaction under the structural disorder intrinsic to this system.

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A. Ino, T. Okane, S. -I. Fujimori, A. Fujimori, T. Mizokawa, Y. Yasui, T. Nishikawa, M. Sato. 2004-05-07. Evolution of the electronic structure from electron-doped to hole-doped states in the two-dimensional Mott-Hubbard system La1.17-xPbxVS3.17. https://doi.org/10.1103/physrevb.69.195116

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