Kondo-like Effect of Atomic Motion on Resistivity in Pb_1−xGe_xTe

Abstract

Kondo-like effect on the low temperature resistivity associated with off-center Ge ions in Pb_1−xGe_xTe is theoretically explored. The tunneling motion of Ge ions between two equivalent sites along the [111] direction is introduced by means of the so-called two-level description. The observed nearly logarithmic temperature dependence of resistivity in Pb_1−xGe_xTe is ascribed to the strong coupling limit of the scaling of the interaction between carriers and the two-level system. In the presence of the structural phase change, the asymmetry of the double-well potential of Ge ions is induced. The freezing of scaling process at the energy comparable to splitting between two-levels leads to a drastic decrease of the logarithmic portion of resistivity below the critical temperature of the structural phase change.