From frustrated insulators to correlated anisotropic metals: charge ordering and quantum criticality in coupled chain systems

TL;DR

This paper investigates the phase diagram of coupled one-dimensional quarter-filled electronic systems, revealing complex charge and spin orders, gapless phases, and quantum critical phenomena driven by inter-chain couplings and fluctuations.

Contribution

It provides a detailed analysis of coupled pseudospin transverse-field Ising models, uncovering new phases and quantum critical points relevant for strongly correlated chain and ladder systems.

Findings

Identification of Wigner/Peierls charge order and Neel/dimer spin order.

Discovery of a stable orbital antiferromagnetic phase.

Observation of a gapless intermediate phase with Kosterlitz-Thouless transitions.

Abstract

A recent study revealed the dynamics of the charge sector of a one-dimensional quarter-filled electronic system with extended Hubbard interactions to be that of an effective pseudospin transverse-field Ising model (TFIM) in the strong coupling limit. With the twin motivations of studying the co-existing charge and spin order found in strongly correlated chain systems and the effects of inter-chain couplings, we investigate the phase diagram of coupled effective (TFIM) systems. A bosonisation and RG analysis for a two-leg TFIM ladder yields a rich phase diagram showing Wigner/Peierls charge order and Neel/dimer spin order. In a broad parameter regime, the orbital antiferromagnetic phase is found to be stable. An intermediate gapless phase of finite width is found to lie in between two charge-ordered gapped phases. Kosterlitz-Thouless transitions are found to lead from the gapless phase to either of the charge-ordered phases. A detailed analysis is also carried out for the dimensional crossover physics when many such pseudospin systems are coupled to one another. Importantly, the analysis reveals the key role of critical quantum fluctuations in driving the strong dispersion in the transverse directions, as well as a T=0 deconfinement transition. Our work is potentially relevant for a unified description of a class of strongly correlated, quarter-filled chain and ladder systems.