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HL: Halbleiterphysik

HL 12: Quantenpunkte und -dr
ähte: Transporteigenschaften II

HL 12.2: Vortrag

Montag, 24. März 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 T_K 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 T_K on U and the ratio of tunneling amplitudes is discussed.