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TT: Tiefe Temperaturen

TT 4: Correlated Electrons: Quantum Impurities, Kondo Physics

TT 4.3: Talk

Monday, March 27, 2006, 11:45–12:00, HSZ 301

Transmission phase through a two-level quantum dot — •Theresa Hecht¹, Yuval Oreg², and Jan von Delft¹ — ¹Department für Physik, CeNS and Arnold Sommerfeld Center, Ludwig-Maximilians Universität München, Germany — ²Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, Israel

The recent measurements of Schuster et al. [1] of the transmission phase through a quantum dot embedded in one arm of an Aharonov Bohm interferometer contradict the simple models that were used to describe the phase evolution so far, see e.g. [2]. Inspired by this experiment, we study the transmission phase of a quantum dot embedded in one arm of a two path electron interferometer. Following [3], where it was shown that in a two-level quantum dot the generic and experimentally realistic condition Γ_upper≠Γ_lower always leads to an occupation inversion, n_upper>n_lower, we study a two-level Anderson model by means of Wilson’s numerical renormalization group method. Relating the scattering phase and the occupation of the levels at T=0 using the Friedel sum rule, we can explain that for Γ_upper≠Γ_lower, the transmission always experiences a phase lapse of π as a function of gate voltage, independent of the parameters of the quantum dot or the parity of the levels. We investigate both the temperature and magnetic field dependence of the transmission amplitude through the dot.

[1] R. Schuster, E. Buks, M. Heiblum, D. Mahalu, V. Umansky, H. Shtrikman, Nature 385, 417 (1997).

[2] U. Gerland et al., Phys.Rev.Lett. 84, 3710 (2000).

[3] M. Sindel, A. Silva, Y. Oreg, J.von Delft, PRB 72, 125316 (2005).