Giant Nernst Effect in (TMTSF)$_2$PF$_6$

Here we present a detailed study of the Nernst effect in (TMTSF) $_2$PF$_6$, where giant resonant-like Nernst oscillations were found when a magnetic field is aligned with magic angles (inter- chain directions).\footnote{W. Wu et al, PRL 91, 056601 (2003)} The amplitude of Nerst signal is order of 100 $\mu$V/K at H$\sim$7.5T and T$\sim$1K. The Nernst resonance at H//c’ rises gradually as T is lowered, reaches a peak at T$\sim$1K and then falls sharply to zero around 150mK. The Nernst signal is a highly non-linear function of H. This can be partially explained by the large magneto-resistance. The Nernst resonance has a weak pressure dependence. The sign-change of Nernst effect upon rotation through the magic angles suggests that the transport in (TMTSF) $_2$PF$_6$ is effectively coherent only in planes and only when these magic angle planes are parallel to the applied field.