Phase coherence and the Nernst effect at magic angles in organic conductors

TL;DR

This paper proposes a model explaining the giant Nernst signal in (TMTSF)$_2$PF$_6$ near magic angles, attributing it to vortex motion and phase coherence loss in specific planes, aligning with experimental observations.

Contribution

It introduces a novel model linking phase coherence disruption and vortex dynamics to the observed Nernst effect at magic angles in organic conductors.

Findings

Nernst signal varies with tilt angle of magnetic field.

Resistance notches are explained by flux-flow dissipation.

Model aligns with experimental data on vortex behavior.

Abstract

A giant Nernst signal was recently observed for fields near crystallographic directions in (TMTSF)$_2$PF$_6$. Such large Nernst signals are most naturally associated with the motion of pancake vortices. We propose a model in which phase coherence is destroyed throughout the sample except in planes closely aligned with the applied field $\bf H$. A small tilt above or below the plane changes the direction and density of the penetrating vortices and leads to a Nernst signal that varies with the tilt angle of $\bf H$ as observed. The resistance notches at magic angles are understood in terms of flux-flow dissipation from field-induced vortices.