# Mesoscopic Kondo Problem

### Ribhu K. Kaul 1, Denis Ullmo 1, 2, Shailesh Chandrasekharan 1, Harold U. Baranger 1

#### Europhysics Letters (EPL) 71 (2005) 973-979

We study the effect of mesoscopic fluctuations on a magnetic impurity coupled to a spatially confined electron gas with a temperature in the mesoscopic range (i.e. between the mean level spacing $\\Delta$ and the Thouless energy $E_{\\rm Th}$). Comparing poor-man\'s scaling\'\' with exact Quantum Monte Carlo, we find that for temperatures larger than the Kondo temperature, many aspects of the fluctuations can be captured by the perturbative technique. Using this technique in conjunction with semi-classical approximations, we are able to calculate the mesoscopic fluctuations for a wide variety of systems. For temperatures smaller than the Kondo temperature, we find large fluctuations and deviations from the universal behavior.

• 1. Department of Physics,
Duke University
• 2. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
CNRS : UMR8626 – Université Paris XI - Paris Sud