Spin-Density-Wave Phase Transitions in Quasi-One-Dimensional Dimerized Quarter-Filled Organic Conductors

TL;DR

This study investigates the spin density wave phase transitions in quasi-one-dimensional dimerized quarter-filled organic conductors, revealing a critical interchain hopping value that separates incoherent metal and Fermi liquid regimes, and proposing a comprehensive phase diagram.

Contribution

The paper introduces a phase diagram for SDW transitions in dimerized quarter-filled conductors using renormalization-group and RPA methods, highlighting the role of intrachain umklapp scattering.

Findings

Existence of a critical interchain hopping value separating regimes.

SDW transition driven by intrachain umklapp scattering.

Proposed phase diagram covering both incoherent and Fermi liquid regimes.

Abstract

We have studied spin density wave (SDW) phase transitions in dimerized quarter-filled Hubbard chains weakly coupled via interchain one-particle hopping, $t_{b0}$. It is shown that there exists a critical value of $t_{b0}$, $t_{b}^\ast$, between the incoherent metal regime ($t_{b0}<t_{b}^\ast$) and the Fermi liquid regime ($t_{b0}>t_{b}^\ast$) in the metallic phase above the SDW transition temperature. By using the 2-loop perturbative renormalization-group approach together with the random-phase-approximation, we propose a SDW phase diagram covering both of the regimes. The SDW phase transition from the incoherent metal phase for $t_{b0}<t_{b}^\ast$ is caused by growth of the intrachain electron-electron umklapp scattering toward low temperatures, which is regarded as preformation of the Mott gap. We discuss relevance of the present result to the SDW phase transitions in the quasi-one-dimensional dimerized quarter-filled organic conductors, (TMTTF)$_2$X and (TMTSF)$_2$X.