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HL: Halbleiterphysik
HL 2: Symposium: Kondo Physics in Quantum Dots
HL 2.2: Fachvortrag
Monday, March 26, 2001, 11:00–11:30, S2
Unitary Limit Kondo Effect at finite Magnetic Fields — •W.G. van der Wiel1, S. De Franceschi1, J. Motohisa2, J.M. Elzerman1, T. Fujisawa3, S. Tarucha3,4, and L.P. Kouwenhoven1 — 1Department of Applied Physics, DIMES, and ERATO Mesoscopic Correlation Project, Delft University of Technology, PO Box 5046, 2600 GA Delft, The Netherlands — 2Research Center for Interface Quantum Electronics, Hokkaido University, Sapporo, Japan — 3NTT Basic Research Laboratories, Atsugi-shi, Kanagawa 243-0198, Japan — 4ERATO Mesoscopic Correlation Project, University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan
We observe a strong Kondo effect in a semiconductor quantum dot when a small magnetic field (B < 0.4 T) is applied. The Coulomb blockade for electron tunneling is overcome completely by the Kondo effect and the conductance reaches the unitary-limit value 2e2/h [1]. We compare the experimental Kondo temperature with the theoretical predictions for the spin-1/2 Anderson impurity model. Excellent agreement is found throughout the Kondo regime. Phase coherence is preserved when a Kondo quantum dot is included in one of the arms of an Aharonov-Bohm ring structure and the phase behavior differs from previous results on a non-Kondo dot. Recent results obtained at higher magnetic field (B > 4.5 T), show that also in this regime the unitary limit can be reached in combination with a Kondo temperature of several Kelvin.
[1] W.G. van der Wiel, S. De Franceschi, T. Fujisawa, J.M. Elzerman, S. Tarucha and L.P. Kouwenhoven, Science 289, 2105 (2000).