Lundi 13 août 2012 à 10h15
Salle 234, Ecole de Physique

The role of multi-resonant states in ac transport

Jian Wang, Department of Physics, The University of Hong Kong

In this talk, we will discuss our recent work on emittance in the presence of Anderson disorders. It is well known that for a specific mesoscopic sample, the emittance is negative (inductive like response) when the system is very transmissive but is positive (capacitive like) when the transmission coefficient is small. As a result, it is expected that for a collection of random mesoscopic samples, the average emittance should be negative when the system is in the ballistic or quasi-ballistic regime at small disorder strength. At large disorders, however, the system is in the diffusive or even localized regime, the emittance should be positive. Indeed, theoretical result obtained from random matrix theory or diagrammatic perturbation theory agrees with this expectation for a chaotic quantum dot system. However, our numerical results for a tight-binding system with Anderson disorders show that the average emittance is always negative regardless of the disorder strength, i.e., the emittance is negative when system is in ballistic, diffusive, and even in the localized regimes. Our analysis suggests that this counter-intuitive result is due to the appearance of non-diffusive elements in the system, the necklace states (or the precursor of necklace states in the diffusive regime) whose existence has been confirmed experimentally in an optical system.