Quantum computing and condensed matter physics with microwave photons

Kondo Effect in Electromigrated Gold Break Junctions

A. A. Houck, J. Labaziewicz, E. K. Chan, J. A. Folk, and I. L. Chuang

We present gate-dependent transport measurements of Kondo impurities in bare gold break junctions, generated with high yield using an electromigration process that is actively controlled. Thirty percent of measured devices show zero-bias conductance peaks. Temperature dependence suggests Kondo temperatures 7 K. The peak splitting in magnetic field is consistent with theoretical predictions for g = 2, though in many devices the splitting is offset from 2gμBby a fixed energy. The Kondo resonances observed here may be due to atomic-scale metallic grains formed during electromigration.