Optical Conductivity Measurement of a Dimer-Mott to Charge-Order Phase Transition in a Two-Dimensional Quarter-Filled Organic Salt Compound

Abstract

We report a novel insulator-insulator transition arising from the internal charge degrees of freedom in the two-dimensional quarter-filled organic salt beta-(meso-DMBEDT-TTF)2PF6. The optical conductivity spectra above Tc = 70 K display a prominent feature of the dimer-Mott insulator, characterized by a substantial growth of a dimer peak near 0.6 eV with decreasing temperature. The dimer-peak growth is rapidly quenched as soon as a peak of the charge order shows up below Tc, indicating a competition between the two insulating phases. Our infrared imaging spectroscopy has further revealed a spatially competitive electronic phases far below Tc, suggesting a nature of quantum phase transition driven by material-parameter variations.

5 pages, 4 figures, supplemental material, to be published in Phys. Rev. Lett

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Cited by in corpus (6)

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• Application of Bruggeman and Maxwell Garnett homogenization formalisms to random composite materials containing dimers
• Electronic correlations and spin frustration in the molecular conductors $\kappa$-(BEDT-TTF)${}_2$X probed by magnetic quantum oscillations