Kondo effect in multiple quantum dots and deformable molecules

Anton Ramsak

Faculty of Mathematics and Physics, University of Ljubljana, Ljubljana, Slovenia

Among multiple quantum dot systems chains with Hubbard or electron-phonon interaction and with even or odd number of sites behave quite differently:

(1) In double quantum dots with finite both inter-dot tunneling and inter-dot repulsive capacitive coupling the results reveal the competition between extended Kondo phases and local singlet phases in spin and charge degrees of freedom. The corresponding phase diagram is determined quantitatively.

(2) In comparison with double dot systems the results for serially coupled triple quantum dots reveal an interplay between magnetic ordering, charge fluctuations and the tendency of itinerant electrons in the leads to screen magnetic moments. Resulting novel Kondo phases will be presented in a phase diagram which can be sampled by measuring the zero-bias conductance.

(3) Molecules with Coulomb interaction and with various types of phonon modes exhibit spin and isospin Kondo effect. As an example will be presented an analysis of conductance together with local occupation, local moment, charge fluctuations and fluctuations of molecular deformation. Deformation fluctuations are quantitatively related to charge fluctuations which exhibit similarity also to static charge susceptibility.

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