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Issue 5, 2018
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Pressure-induced Mott-insulator–metal crossover at ambient temperature in an overexpanded fulleride

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Abstract

Rb0.5Cs2.5C60 is a member of the family of face-centred-cubic (fcc)–structured alkali fullerides, A3C60 (A = alkali metal) with a highly expanded lattice size. At ambient temperature and pressure, it is a Mott–Jahn–Teller insulator. However, upon cooling it exhibits first a crossover to an anomalous metallic state (Jahn–Teller metal) in the vicinity of 90 K followed next by a transition to a bulk superconductor with a transition temperature, Tc of 29.4 K. Here we study its structural and electronic response to the application of pressure. Synchrotron X-ray powder diffraction at ambient temperature shows that the same Mott-insulator–metal electronic state crossover can be induced through pressure application under isothermal conditions, as evidenced by a distinct broad symmetry-preserving compressibility anomaly, which sets in at ∼0.4 GPa and extends to ∼0.75 GPa. Complementary magnetic susceptibility measurements also reveal that the crossover temperature, T′ tunable at ambient pressure through adjusting the dopant ratio to vary the unit cell volume, can be controlled through pressure application and be mapped onto the same global electronic phase diagram. The observed electronic response, as a function of both physical and ‘chemical’ pressure, is thus of the same electronic origin, namely the control of the bandwidth, W via outer wave function overlap of the constituent fulleride ions.

Graphical abstract: Pressure-induced Mott-insulator–metal crossover at ambient temperature in an overexpanded fulleride

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Publication details

The article was received on 29 Jan 2018, accepted on 13 Mar 2018 and first published on 14 Mar 2018


Article type: Research Article
DOI: 10.1039/C8QM00048D
Citation: Mater. Chem. Front., 2018,2, 993-998
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    Pressure-induced Mott-insulator–metal crossover at ambient temperature in an overexpanded fulleride

    R. H. Zadik, Y. Takabayashi, R. H. Colman, G. Garbarino and K. Prassides, Mater. Chem. Front., 2018, 2, 993
    DOI: 10.1039/C8QM00048D

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