 
Summary: Enhancement of the Twochannel Kondo Eect in SingleElectron boxes
Frithjof B. Anders
Institut fur Festkorperphysik, Technical University Darmstadt, 64289 Darmstadt, Germany
Eran Lebanon and Avraham Schiller
Racah Institute of Physics, The Hebrew University, Jerusalem 91904, Israel
We investigate the charging of quantum box connected to a lead through a single electron transis
tor near the degeneracy point in the Coulomb blockade regime. The lowtemperature Hamiltonian is
solved exactly for arbitray gate voltages, temperature, level positions of the single electron transistor
and tunneling probability to the single electron transistor using Wilson's numerical renormalization
group. The numerical results are supported by analytical second order RG solved analytically in
weak coupling. The physics is governed by a twochannel Kondo xed point re
ected in a loga
rithmically divergent eective capacitance at the degenercy point. The twochannel Kondo eect is
robust with repect to shifting the resonace of the SET and the inclusion of a onsite Coulomb re
pulsion. Its characteristic energy scale TK is no longer exponentially small when the single electron
transistor approaches perfect transmission.
PACS numbers: PACS numbers: 73.23.Hk, 72.15.Qm, 73.40.Gk
I. INTRODUCTION
The twochannel Kondo eect 1,2 is a prototype for non
Fermiliquid behavior in correlated electron systems. It
occurs when a spin 1
