Antiresonances as precursors of decoherence

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: 9 November 2005

Abstract

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.