Isotope effect, pressure dependence and random field smearing of the proton glass transition

Abstract

Abstract The phase diagram of the proton glass Rb1−x(NH4)x H2PO4 has been evaluated as a function of composition, pressure and amount of deuteration within a random bond version of the Ising model in a transverse field and a replica symmetric mean field approach. It is shown that the presence of Gaussian random fields with zero mean and variance Δ results in a smearing of the proton glass transition, i.e. the cusp in the dielectric susceptibility is rounded off and the proton glass order parameter remains finite at temperatures far above the nominal freezing temperature.