Coherent resonant transport through a mesoscopic system with quantum ac microwave field
Department of Physics, The University of Hong Kong,
Pokfulam Road, Hong Kong, China
2 Department of Physics, Beijing Institute of Technology, Beijing 100081, China
Published online: 15 June 1999
The time-dependent transport through an ultrasmall quantum dot coupling to two electron reservoirs is investigated. The quantum dot is perturbed by a quantum microwave field (QMF) through gate. The tunneling current formulae are obtained by taking expectation values over coherent state (CS), and SU(1,1) CS. We derive the transport formulae at low temperature by employing the nonequilibrium Green function technique. The currents exhibit coherent behaviors which are strongly associated with the applied QMF. The time-dependent currents appear compound effects of resonant tunneling and time-oscillating evolution. The time-averaged current and differential conductance are calculated, which manifest photon-assisted behaviors. Numerical calculations reveal the similar properties as those in classical microwave field (CMF) perturbed system for the situations concerning CS and squeezed vacuum SU(1,1) CS. But for other squeezed SU(1,1) CS, the tunneling behavior is quite different from the system perturbed by a single CMF through gate. Due to the quantum signal perturbation, the measurable quantities fluctuate fiercely.
PACS: 73.40.-c – Electronic transport in interface structures / 73.20.Dx – Electron states in low-dimensional structures (superlattices, quantum well structures and multilayers) / 72.10.Bg – General formulation of transport theory
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 1999