Kondo temperature dependence of the Kondo splitting in a single-electron transistor

A Kondo peak in the differential conductance of a single-electron transistor is measured as a function of both the magnetic field and the Kondo temperature. We observe that the Kondo splitting decreases logarithmically with the Kondo temperature and that there exists a critical magnetic field B-C below which the Kondo peak does not split, in qualitative agreement with theory. However, we find that the magnitude of the prefactor of the logarithm is larger than predicted and is independent of B, in contradiction with theory. Our measurements also suggest that the value of B-C is smaller than predicted.