Antiresonances as precursors of decoherenceL. E. F. Foa Torres1, H. M. Pastawski2 and E. Medina3
1 International Center for Theoretical Physics - Strada Costiera 11, 34014 Trieste, Italy
2 Facultad de Matemática, Astronomía y Física, Universidad Nacional de Córdoba Ciudad Universitaria, 5000 Córdoba, Argentina
3 Centro de Física, Instituto Venezolano de Investigaciones Científicas Apartado 21827, Caracas 1020A, Venezuela
received 26 September 2005; accepted in final form 9 November 2005
published online 7 December 2005
We show that, in the presence of a complex spectrum, antiresonances act as a precursor for dephasing enabling the crossover to a fully decoherent transport even within a unitary Hamiltonian description. This general scenario is illustrated here by focusing on a quantum dot coupled to a chaotic cavity containing a finite, but large, number of states using a Hamiltonian formulation. For weak coupling to a chaotic cavity with a sufficiently dense spectrum, the ensuing complex structure of resonances and antiresonances leads to phase randomization under coarse graining in energy. Such phase instabilities and coarse graining are the ingredients for a mechanism producing decoherence and thus irreversibility. For the present simple model one finds a conductance that coincides with the one obtained by adding a ficticious voltage probe within the Landauer-Büttiker picture. This sheds new light on how the microscopic mechanisms that produce phase fluctuations induce decoherence.
03.65.Yz - Decoherence, open systems; quantum statistical methods.
73.50.Bk - General theory, scattering mechanisms.
73.40.Gk - Tunneling.
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