Dresden 2003 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 20: Postersitzung IV (Mesoskopische Systeme, Supraleitung: Massivmaterialien, Bandleiter, Pinning, Vortexdynamik, Transporteigenschaften, Korngrenzen)

TT 20.14: Poster

Donnerstag, 27. März 2003, 14:30–19:00, P2c, P2d

Persistent currents in mesoscopic rings coupled to a reservoir — •Bernhard Wunsch and Alexander Chudnovskiy — I. Institut für Theoretische Physik, Universität Hamburg,Jungiusstr. 9, 20355 Hamburg

Persistent currents rely on quantum coherence and their stability against perturbation is a basic question. We study the persistent current in an ideal mesoscopic ring and introduce decoherence by coupling it to a reservoir of fermionic states. The coupling is described by a tunneling operator, that does not conserve the angular quantum number. Within this model both the strength of coupling and the number of ring states coupled to the reservoir can be varied.

In the regime of strong coupling to the reservoir, long-living states develop that are localised in the ring. These states show up as sharp peaks in the density of states. The simplified model, which only considers the coupling of two ring states to the reservoir could be solved analytically by diagonalizing the effective Hamiltonian. In the strong coupling limit one state decouples completely from the reservoir.

The dependence of the persistent current on the number of coupled levels shows a pronounced even-odd asymmetry in the strong coupling regime. Even in the limit of strong coupling the persistent current is only completely suppressed, if all ring states are coupled to the reservoir.