Harvard Condensed Matter Theory Seminars

Abstract

Ganpathy Murthy, University of Kentucky

Interplay between Kondo screening and Stoner interactions in a quantum dot

The Kondo effect, where a sea of conduction electrons screens the spin of a magnetic impurity, is the simplest and best understood strongly correlated state. Recent advances in nanotechnology have made it possible to realize the impurity spin as a small quantum dot with an odd number of electrons, and the Kondo effect when the dot is coupled to the leads has been measured. Another experiment goes further and makes the conduction electrons themselves live on a large dot. It turns out that electrons confined to a chaotic dot generically interact with each other via interactions which can be characterized at low energies by a charging energy and a Stoner interaction. There is a competition between the Kondo interaction, which wants the electrons on the large dot to form a screening cloud, and the Stoner interaction, which wants the electrons to be spin polarized. This interplay leads to some surprising effects which will be discussed.