Metal-insulator and insulator-insulator transitions in the quarter-filled band organic conductors

TL;DR

This paper revisits the theory of electronic instabilities in quarter-filled organic conductors, highlighting how electron correlations influence phase angles and charge density wave stability, which explains phase weakening in superconducting states.

Contribution

It provides new insights into phase angle switching of density waves and the destabilization of charge density waves in quasi-two-dimensional regimes.

Findings

Phase angles of density waves change with electron correlation.

Intersite Coulomb interactions must be below a critical value.

Charge density waves weaken in the quasi-two-dimensional regime.

Abstract

The theory of the 2k_F and 4k_F instabilities in quarter-filled band organic conductors is revisited. The phase angles of the 2k_F bond and charge density waves are shown to change as electron correlation is turned on, and this switching of the phase angle is critical for understanding the bond distortion patterns in the real materials. Intersite Coulomb interactions in the real materials must be nonzero but less than a critical value. Both intersite and intrasite charge density waves are destabilized in the quasi-two-dimensional regime for realistic parameters, thus explaining the weakening of these phases in the superconducting materials.