Motivated by experiments on double quantum dots, we study the problem of a single magnetic impurity confined in a finite metallic host. We prove an exact theorem for the ground state spin, and use analytic and numerical arguments to map out the spin structure of the excitation spectrum of the many-body Kondo-correlated state, throughout the weak to strong coupling crossover. These excitations can be probed in a simple tunneling-spectroscopy transport experiment; for that situation we solve rate equations for the conductance.
@article{arxiv.cond-mat/0601274,
title = {Spectroscopy of the Kondo Problem in a Box},
author = {Ribhu K. Kaul and Gergely Zaránd and Shailesh Chandrasekharan and Denis Ullmo and Harold U. Baranger},
journal= {arXiv preprint arXiv:cond-mat/0601274},
year = {2007}
}