%0 Journal Article
%T Electrodynamics of Bechgaard Salts: Optical Properties of One-Dimensional Metals
%A Martin Dressel
%J ISRN Condensed Matter Physics
%D 2012
%R 10.5402/2012/732973
%X The electrodynamic properties of the quasi-one-dimensional organic conductors (TMTSF)2X are discussed, with particular emphasis on important deviations from the simple Drude model, the transition from a Luttinger-liquid to a Fermi-liquid behavior at the dimensional crossover when pressure is applied or temperature reduced, indications of a pseudogap as well as a low-frequency collective mode. Superconductivity and spin-density-wave ground states breaking the symmetry and gaps should occur in the excitation spectra. The previous literature is summarized and the current status of our understanding presented. Novel THz experiments on (TMTSF)2PF6 and (TMTSF)2ClO4 not only shine light into some of the open questions, but also pose new ones. 1. Introduction Physics in one dimension is a fascinating topic for theory and challenging for experiments. One-dimensional models are simpler compared to three-dimensional ones; in many cases, analytical solutions exist only in one dimension, while numerical approaches have to be used in higher dimensions [1]. Often the reduction of dimensionality does not really matter because the essential physics remains unaffected. But there are also a number of phenomena in condensed matter which only or mostly occur in one dimension. In general, the dominance of the lattice is reduced and electronic interactions become superior. This implies that physics in reduced dimensions is physics of low energies; the relevant effects do not occur in the electron-volt range but at millielectron volts and below. Quantum mechanical effects are essential as soon as the confinement approaches the electron wavelength. Fundamental concepts of physics, like the Fermi liquid theory of interacting particles breaks down in one dimension and has to be replaced by alternative concepts based on collective excitations [2]. One-dimensional structures are intrinsically unstable for thermodynamic reasons. Hence various kinds of ordering phenomena may take place which break the translational symmetry of the lattice, charge, or spin degrees of freedom: phase transitions occur as a function of temperature or some order parameter. On the other hand, fluctuations suppress long-range order at any finite temperature in one (and two) dimension. The ordered ground state is only stabilized by the fact that real systems consist of one-dimensional chains, which are coupled to some degree. The challenge now is to extract the one-dimensional physics from experimental investigations of quasi-one-dimensional systems and to check the theoretical predictions. Besides pure
%U http://www.hindawi.com/journals/isrn.cmp/2012/732973/