INFLUENCE OF IMPURITIES ON KINK DYNAMICS IN CRYSTALS WITH HIGH PEIERLS BARRIERS

The problem of kink depinning from fluctuating point obstacle in a vis cous gas of quasiparticle excitations of a crystal is considered. It i s shown that at infinitely small friction the depinning act is determi ned mainly by the stochastic behavior of the kink. However, the fluctu ational dynamics of the obstacle becomes significant in crystals with heavy lattice atoms and light impurity, in the presence of sufficientl y abrupt kinks. The role of impurities in the depinning process at fin ite frictional coefficient is analyzed.