Modulated-impurity mechanism of pinning in KCP

Abstract
A modulated-impurity (MI) mechanism of pinning is put forward for K2Pt(CN)4Br0.3*3.2H2O (KCP) based on the Q-quasi-modulated distribution of the bromine anions along the chain axis (Q/2 being the Fermi momentum reduced to the first Brillouin zone). The spectrum of the collective excitations (amplitudons and phasons) as well as the dielectric function are calculated for the charge density wave (CDW) state. Fair agreement is obtained with the optical and neutron scattering data in KCP. A possible explanation is suggested of the difference between the DC gap and the optical one.