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

摘要

A giant Nernst signal was recently observed for fields near crystallographic directions in (TMTSF)(2)PF6. 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 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 H as observed. The resistance notches at magic angles are understood in terms of flux-flow dissipation from field-induced vortices.