Mechanism of CDW-SDW Transition in One Dimension

TL;DR

This paper investigates the phase transition mechanisms between charge-density-wave and spin-density-wave phases in a one-dimensional extended Hubbard model, revealing a separate third phase and analyzing transition types through spectral and symmetry methods.

Contribution

It provides a detailed analysis of the CDW-SDW transition, demonstrating the existence of an intermediate phase and clarifying the nature of the phase transitions in the model.

Findings

Gaussian and spin-gap transitions occur separately in the weak to intermediate coupling.

A third phase exists between the CDW and SDW states.

Results align with strong-coupling perturbation and order parameter evaluations.

Abstract

The phase transition between charge- and spin-density-wave (CDW, SDW) phases is studied in the one-dimensional extended Hubbard model at half-filling. We discuss whether the transition can be described by the Gaussian and the spin-gap transitions under charge-spin separation, or by a direct CDW-SDW transition. We determine these phase boundaries by level crossings of excitation spectra which are identified according to discrete symmetries of wave functions. We conclude that the Gaussian and the spin-gap transitions take place separately from weak- to intermediate-coupling region. This means that the third phase exists between the CDW and the SDW states. Our results are also consistent with those of the strong-coupling perturbative expansion and of the direct evaluation of order parameters.