Eur. Phys. J. B 46, 223-230 (2005)
https://doi.org/10.1140/epjb/e2005-00223-3

Anisotropy and field-dependence of the spin-density-wave dynamics in the quasi one-dimensional conductor (TMTSF)PF

¹ 1. Physikalisches Institut, Universität Stuttgart, Pfaffenwaldring 57, 70550 Stuttgart, Germany
² Institut za fiziku, P.O. Box 304, HR-10001 Zagreb, Croatia

Corresponding author: ^a dressel@pil.physik.uni-stuttgart.de

Received: 3 December 2004
Revised: 14 February 2005
Published online: 19 July 2005

Abstract

The anisotropic and non-linear transport properties of the quasi one-dimensional organic conductor (TMTSF)₂PF₆ have been studied by dc, radiofrequency, and microwave methods. Microwave experiments along all three axes reveal that collective transport, which is considered to be the fingerprint of the spin-density-wave condensate, also occurs in the perpendicular direction. The pinned mode resonance is present in the a and -axes response, but not along the least conducting c^* direction. The ac-field threshold, above which the spin-density-wave response is non-linear, strongly decreases as the temperature drops below 4 K. With increasing strength of the microwave electric field and of the radiofrequency signal, the pinned mode and the screened phason loss-peak shift to lower frequencies. In the non-linear regime, in addition to the phason relaxation mode with Arrhenius-like resistive decay, an additional mode with very long and temperature-independent relaxation time appears below 4 K. We attribute the new process to short-wavelength excitations associated with discommensurations of the spin density wave close to commensurability.