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Charge ordering and coexistence of charge fluctuations in quasi-two-dimensional organic conductors $θ$-(BEDT-TTF)$_2X$

Masafumi Udagawa·Yukitoshi Motome
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Abstract

We present a scenario for the peculiar coexistence of charge fluctuations observed in quasi-2D 1/4-filled organic conductors $θ$-(BEDT-TTF)$_2X$ in the quantum critical regime where the charge ordering is suppressed down to zero temperature. The scenario is explored in the extended Hubbard model including electron-phonon couplings on an anisotropic triangular lattice. We find that the coexisting fluctuations emerge from two different instabilities, the ``Wigner crystallization on lattice'' driven by the off-site Coulomb repulsion and the charge-density-wave formation due to the nesting of the Fermi surface, not from phase competition or real-space inhomogeneity. This mechanism explains the contrastive temperature dependence of two fluctuations in experiments.

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Masafumi Udagawa, Yukitoshi Motome. 2007-05-17. Charge ordering and coexistence of charge fluctuations in quasi-two-dimensional organic conductors $θ$-(BEDT-TTF)$_2X$. https://doi.org/10.1103/physrevlett.98.206405

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