Condensed Matter Seminar

Harold Baranger
Duke University

Thursday, October 5, 2006
1:00 pm in SPL 52

Correlations in Quantum Dots: Kondo and Wigner Crystal

Abstract: Quantum dots have provided a fruitful setting in which to probe electron-electron interactions in recent years. I will discuss two possible further examples: (1) Spectroscopy of the Kondo problem in a box-- Motivated by experiments on double quantum dots, we studied the problem of a single magnetic impurity confined in a finite metallic host. The spin structure of the excitations of the many-body Kondo-correlated state is mapped out throughout the weak to strong coupling crossover using analytic and numerical arguments. These excitations can be probed in a simple tunneling-spectroscopy transport experiment. (2) Correlation induced inhomogeneity in circular quantum dots-- In order to probe the development of Wigner crystal correlations in a tunable finite system, we studied the electron gas confined to a circular disc. Using quantum Monte Carlo techniques, we show that the electron-electron correlation induced by an increase of the interaction first smoothly causes rings, and then angular modulation, without any signature of a sharp transition in this density range. This suggests that inhomogeneities in a confined system, which exist even without interactions, are significantly enhanced by correlations.