Berlin 2005 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 34: Correlated Electrons - Quantum Impurities, Kondo Physics

TT 34.1: Vortrag

Mittwoch, 9. März 2005, 09:45–10:00, TU H104

Frequency-dependent transport through a quantum dot in the Kondo regime — •Michael Sindel¹, Walter Hofstetter², Jan von Delft¹, and Markus Kindermann³ — ¹Physics Department and Center for NanoScience, LMU München, 80333 München — ²Institut für Theoretische Physik A, RWTH Aachen, 52056 Aachen — ³Department of Physics, Massachusetts Institute of Technology, Cambridge MA 02139, USA

Motivated by experiments of Kogan et al. [1] we study the AC conductance and equilibrium current fluctuations of a Coulomb blockaded quantum dot in the Kondo regime. To this end we apply the nonperturbative numerical renormalization group method in combination with the Kubo formalism [2] suitable for the nonperturbative calculation of finite-frequency transport properties. For frequencies smaller than the charge excitation energy min{|є_d|,|U+є_d|} we derive a formula for the frequency dependent current by extending [3]. This formula enables us to relate the spectral function with the linear AC conductance and the frequency-dependent equilibrium current fluctuations, respectively. We demonstrate that AC transport provides a new route to measuring the equilibrium spectral density (a key signature of Kondo physics) which so far has defied direct experimental observation.
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W. Izumida, O. Sakai, and Y. Shimizu, J. Phys. Soc. Jpn. 66, 717 (1997).
A.-P. Jauho, N.S. Wingreen and Y. Meir, Phys. Rev. B 50, 5528 (1994).