Dresden 2003 – scientific programme
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HL: Halbleiterphysik
HL 12: Quantenpunkte und -dr
ähte: Transporteigenschaften II
HL 12.2: Talk
Monday, March 24, 2003, 15:30–15:45, POT/81
Enhancement of the Two-channel Kondo Effect in Single-Electron boxes — •Frithjof Anders1, Eran Lebanon2, and Avraham Schiller2 — 1Institut für Festkörperphysik, TU Darmstadt,64289 Darmstadt, Germany — 2Racah Institute of Physics, The Hebrew University, Jerusalem 91904, Israel
A quantum box connected to a lead through a single resonant level is investigated near the degeneracy point of two charge configurations in the Coulomb blockade regime. The effective Hamiltonian obtained via Matveev’s mapping is exactly solved using Wilson’s numerical renormalization group (NRG) method. The effective capacitance of the box at the degeneracy point for a resonant level at the Fermi energy diverges logarithmically, a signature of two-channel Kondo physics. We find that the associated low energy scale TK depends exponentially on the ratio of the two tunneling amplitudes and is strongly enhanced close to perfect transmission. The position of the degeneracy point of the charge step is shifted as function of the resonant level position. We find good agreement of its location with predictions of an analytical second order RG calculations. We show that the two-channel Kondo physics at the degeneracy point is robust against inclusion of a finite Coulomb repulsion U in the case of particle-hole symmetric. The dependence of TK on U and the ratio of tunneling amplitudes is discussed.