2-channel Kondo scaling in conductance signals from 2 level tunneling systems

Abstract

The temperature (T) and voltage (V) dependence of conductance signals in metal point contacts, previously asserted to be due to 2-channel Kondo scattering from atomic 2 level tunneling systems, collapse onto a universal scaling curve dependent on eV/${\mathit{k}}_{\mathit{B}}$T, for all T and eV/${\mathit{k}}_{\mathit{B}}$ below a characteristic Kondo scale. Measurements determine a conductance exponent of 1/2, as expected from conformal field theory solution of the 2-channel Kondo model. The magnetic field (H) dependence at low T is nonanalytic at H=0 (\ensuremath{\propto}\ensuremath{\Vert}H\ensuremath{\Vert}) in contrast to Fermi-liquid theory but in agreement with conformal field theory.