Thermal fluctuations of the order parameter in charge-density waves

Abstract

Incorporating the thermal fluctuations of the phase of charge-density-wave order parameter into the theory, we extend the Fukuyama-Lee-Rice theory to finite temperatures. We find the temperature dependence of the threshold field at low temperatures (e.g., T(1/2)${T}_{c}$) is given by , where ${T}_{0}$ is a material constant independent of the impurity concentration. Furthermore, we find the characteristic Lee-Rice correlation length depends on the temperature as . The former prediction describes quite well the observed temperature dependence of the threshold field ${E}_{T}$(T) at low temperatures of ${\mathrm{NbSe}}_{3}$, orthorhombic and monoclinic ${\mathrm{TaS}}_{3}$, and (${\mathrm{TaSe}}_{4}$${)}_{2}$I. Furthermore, the present theory describes qualitatively both the observed pressure dependence of ${E}_{T}$(0) and ${T}_{0}$ orthorhombic ${\mathrm{TaS}}_{3}$ and (${\mathrm{TaSe}}_{4}$${)}_{2}$I.