arXiv subjects

M. Ţolea

Publications and source records attributed to M. Ţolea.

3 recordsLinked to original sources

arXiv2011

Coulomb oscillations of the Fano-Kondo effect and zero bias anomalies in the double dot meso-transistor

We investigate theoretically the transport properties of the side-coupled double quantum dots in connection with the experimental study of Sasaki {\it et al.} Phys.Rev.Lett.{\bf 103}, 266806 (2009). The novelty of the set-up consists in connecting the Kondo dot directly to the leads, while the side dot provides an interference path which affects the Kondo correlations. We analyze the oscillations of the source-drain current due to the periodical Coulomb blockade of the many-level side-dot at the variation of the gate potential applied on it. The Fano profile of these oscillations may be controlled by the temperature, gate potential and interdot coupling. The non-equilibrium conductance of the double dot system exhibits zero bias anomaly which, besides the usual enhancement, may show also a suppression (a dip-like aspect) which occurs around the Fano {\it zero}. In the same region, the weak temperature dependence of the conductance indicates the suppression of the Kondo effect. Scaling properties of the non-equilibrium conductance in the Fano-Kondo regime are discussed. Since the SIAM Kondo temperature is no longer the proper scaling parameter, we look for an alternative specific to the double-dot. The extended Anderson model, Keldysh formalism and equation of motion technique are used.

cond-mat.mes-hall↗

arXiv2010

Analyzing the measured phase in the multichannel Aharonov-Bohm interferometer

We address the quantum dot phase measurement problem in an open Aharonov-Bohm interferometer, assuming multiple transport channels. In such a case, the quantum dot is characterized by more than one intrinsic phase for the electrons transmission. It is shown that the phase which would be extracted by the usual experimental method (i.e. by monitoring the shift of the Aharonov-Bohm oscillations, as in Schuster {\it et al.}, Nature {\bf 385}, 417 (1997)) does not coincide with any of the dot intrinsic phases, but is a combination of them. The formula of the measured phase is given. The particular case of a quantum dot containing a $S=1/2$ spin is discussed and variations of the measured phase with less than $π$ are found, as a consequence of the multichannel transport.

cond-mat.mes-hall↗

arXiv2004

Resonant and coherent transport through Aharonov-Bohm interferometers with coupled quantum dots

A detailed description of the tunneling processes within Aharonov-Bohm (AB) rings containing two-dimensional quantum dots is presented. We show that the electronic propagation through the interferometer is controlled by the spectral properties of the embedded dots and by their coupling with the ring. The transmittance of the interferometer is computed by the Landauer-Büttiker formula. Numerical results are presented for an AB interferometer containing two coupled dots. The charging diagrams for a double-dot interferometer and the Aharonov Bohm oscillations are obtained, in agreement with the recent experimental results of Holleitner {\it et al}. [Phys. Rev. Lett. {\bf 87}, 256802 (2001)] We identify conditions in which the system shows Fano line shapes. The direction of the asymetric tail depends on the capacitive coupling and on the magnetic field. We discuss our results in connection with the experiments of Kobayashi {\it et al} [Phys. Rev. Lett. {\bf 88}, 256806 (2002)] in the case of a single dot.

cond-mat.mes-hall↗