Thesis presented November 03, 2005

Abstract:
We study the effects of Kondo correlations on the transmission phase shift of a quantum dot (QD). This work is motivated by the quantum interferometry experiments carried out these last years which permit to access the phase shift experienced by an electron passing through a quantum dot in both the Kondo and Coulomb blockade regimes. Our analysis is based on scattering theory and Bethe ansatz calculations in the framework of the Anderson model. In the non magnetic state and at low temperature, the phase shift is found to equal the occupancy of the QD in units of Π. This prediction is in excellent agreement with experimental data. We then propose an interpretation of the phase lapses observed when the gate voltage varies, which are either “incomplete” or “complete” depending whether the system is in the Kondo or Coulomb blockade regime. At last we study the spectral density and the phase shift at finite bias voltages and temperatures, within the NCA approximation of the Anderson model expressed in the slave-boson representation, using the Keldysh formalism to tackle the non-equilibrium situation. A qualitative agreement is found with experimental results.  

Keywords:
Kondo effect, quantum dots, phase shift

On-line thesis.