Theory of Phason Drag Effect on Thermoelectricity

TL;DR

This paper investigates how the phason mode in charge density waves influences thermoelectric properties, predicting a large Seebeck coefficient at low temperatures due to phason effects.

Contribution

It provides a theoretical analysis of phason drag effects on thermoelectricity using linear response theory, highlighting the impact of disorder-induced pinning.

Findings

Seebeck coefficient proportional to the square root of resistivity at low temperatures

Opposite sign of thermoelectric response compared to electronic contributions without Peierls gap

Large thermoelectric effects are expected due to phason dynamics in CDW systems

Abstract

Lee, Rice and Anderson, in their monumental paper, have proved the existence of a collective mode describing the coupled motion of electron density and phonons in one-dimensional incommensurate charge density wave (CDW) in the Peierls state. This mode, which represents the coherent sliding motion of electrons and lattice distortions and affects low energy transport properties, is described by the phase of the complex order parameter of the Peierls condensate, leading to Fr\"ohlich superconductivity in pure systems. Once spatial disorder is present, however, phason is pinned and system is transformed into an insulating ground state: a dramatic change. Since phason can be considered as an ultimate of phonon drag effect, it is of interest to see its effects on thermoelectricity, which has been studied in the present paper based linear response theory of Kubo and Luttinger. The result indicates that a large absolute value of Seebeck coefficient proportional to the square root of resistivity is expected at low temperatures k_B T/\Delta <<1 (\Delta: Peierls gap) with opposite sign to the electronic contributions in the absence of Peierls gap.