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The influence of interference on the Kondo effect

University of British Columbia

The Kondo effect, wherein a local magnetic moment is screened via interactions with a continuum of quantum excitations, occurs in quantum dots with an odd number of electrons. By placing a quantum dot in an Aharanov-Bohm interferometer, one is able to probe the effects of electron interference on the manifestation of the Kondo effect. In this thesis, we present a theoretical study of the Kondo effect in a model system of a quantum dot embedded in an Aharanov-Bohm interferometer connected to two conducting leads. By transforming to the scattering basis of the direct inter-lead tunneling, we are able to describe precisely how the Kondo screening of the dot spin occurs. We calculate the Kondo temperature and zero-temperature conductance and find that both are influenced by the Aharanov-Bohm interferometer as well as the electron density in the leads. We also calculate the form of an additional potential scattering term that arises at low energies due to the breaking of particle-hole symmetry. In addition to these analytic results, a numerical renormalization group analysis of the system is presented. We fully describe the influence of the Aharanov-Bohm interferometer on the renormalization group flow of the quantum dot model and obtain strong support for the derived form of the Kondo temperature. A method for extracting the phase shifts of the strong-coupling fixed point from the numerical data is described. These phase shifts are compared with those derived analytically, providing further support for our conclusions.

Text

2010-11-25

Attribution-NonCommercial-NoDerivs 3.0 Unported

http://hdl.handle.net/2429/30149

Physics

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/3.0/