Collective modes in unconventional density waves

TL;DR

This paper explores the collective excitations in unconventional density waves, revealing how phase degrees of freedom influence density correlators and detailing the anisotropic spin susceptibility in USDW.

Contribution

It provides a theoretical analysis of collective modes in UCDW and USDW, including impurity effects and the behavior of spin susceptibility at low temperatures.

Findings

Density correlator returns to normal form due to phase freedom.

Spin susceptibility in USDW remains anisotropic despite no spin density modulation.

In UCDW, spin response diminishes as temperature decreases.

Abstract

We have investigated the collective modes of unconventional charge and spin density waves (UCDW, USDW) in quasi-one dimensional systems in random phase approximation. The density correlator regains its normal state form due to the phase degree of freedom of the condensate. The possible effect of impurities is also discussed. From this, the current-current correlation function is evaluated through charge conservation. The spin susceptibility of USDW remains anisotropic an spite of the lack of any periodic modulation of the spin density. In UCDW, the spin response gets weaker in all three directions as the temperature is lowered.