Dynamical Properties of Quasi-One-Dimensional Conductors: A Phase Hamiltonian Approach

Abstract

Since the realization of quasi-one-dimensional conductors, there have been extensive investigations into the electronic properties of other such low-dimensional systems, both experimentally and theoretically [1–4]. Above all, systems having a Peierls transition [5] have been investigated in detail. The novelty of this Peierls—Frohlich (PF) [6] state lies in the novel possibility of the transport phenomenon being associated with the collective degree of freedom, i.e. the charge density wave (CDW) [7]. In a CDW, electrons follow the periodic lattice distortion adiabatically, resulting in a periodic spatial variation of the self-consistent charge density. Lee, Rice and Anderson [8] have shown that the low-lying excitation of CDW is due to the sliding motion associated with the lattice distortion, which is described by the phase of the complex order parameter, i.e. the periodic lattice distortion. This phase is related to the choice of the origin of coordinates and then to the translational symmetry of the system. Hence this sliding motion, or sliding conductivity, is sensitive to the impurity scattering and the Umklapp scattering [8]. These scattering mechanisms result in impurity and commensurability pinning, respectively, whose various interesting properties have been revealed since that time. In these investigations the phase Hamiltonian, which is the effective Hamiltonian to describe the motion of the phase and is derived from the full Hamiltonian with electron-phonon interactions, has proved very useful [8–12]. Recently anomalous properties typically observed in NbSe3 have also been discussed in a similar context [13, 14] and by Monceau in Part II of this volume.