Giant Angular Dependent Nernst Effect in the Q1D Organic conductor (TMTSF)$_2$PF$_6$

Abstract

We present a detailed study of the Nernst effect N$_{zx}$ in (TMTSF)$_2$PF$_6$ as a function of temperature, magnetic field magnitude and direction and pressure. As previously reported there is a large resonant-like structure as the magnetic field is rotated through crystallographic directions, the Lebed Magic Angles. These Nernst effect resonances strongly suggest that the transport of the system is effectively ``coherent'' only in crystallographic planes along or close to the applied field direction. We also present analytical and numerical calculations of the conductivity and thermoelectric tensors for (TMTSF)$_2$PF$_6$, based on a Boltzmann transport model within the semi-classical approximation. The Boltzmann transport calculation fails to describe the experiment data. We suggest that the answer may lie in field induced decoupling of the strongly correlated chains.