Spectroscopy of the Kondo Problem in a Box

TL;DR

This paper investigates the Kondo effect in a finite metallic system, providing an exact theorem for the ground state spin and analyzing the excitation spectrum across different coupling regimes, with implications for tunneling spectroscopy.

Contribution

It presents an exact theorem for the ground state spin and maps the excitation spectrum of a Kondo-correlated state in a confined system, bridging weak and strong coupling regimes.

Findings

Exact ground state spin theorem established

Mapped excitation spectrum across coupling regimes

Predicted tunneling spectroscopy signatures

Abstract

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.