Moving charge-density waves in K 0.30MoO 3

Abstract

A number of anisotropic materials exhibit non-linear charge transport resulting from a charge-density wave (CDW) that moves in an applied electric field. In these materials the CDW is pinned to the lattice by impurities at low electric fields, but may be depinned by d.c. fields in excess of a threshold value. A moving CDW is a new form of charge transport in a solid and it is associated with a number of interesting non-linear electrical phenomena. These include enhanced d.c. and a.c. conductivity, a periodic response to a d.c. bias, noise, and metastable conductivity states. The ‘blue bronze’ K 0.30MoO 3 has proved to be an interesting material in which to study CDW transport because of its large sample size and large metastable effects. This paper reviews a.c. measurements of the pinned and unpinned CDW in K 0.30MoO 3. In addition, d.c. measurements and X-ray scattering measurements of field-cooled samples are reported. The unifying feature of these measurements is that the non-linear CDW response is dominated by a large number of degrees of freedom. One must therefore view CDW transport as motion of a deformable medium rather than the sliding of a rigid object.