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
\~7K. The peak splitting in magnetic field is consistent with theoretical
predictions for g=2, though in many devices the splitting is offset from 2guB
by a fixed energy. The Kondo resonances observed here may be due to
atomic-scale metallic grains formed during electromigration.Comment: 5 pages, 3 figure