Orbital fluctuations and strong correlations in quantum dots

TL;DR

This paper explores how orbital degeneracies and charge fluctuations in quantum dots lead to exotic strongly correlated phenomena like SU(4) Kondo effect and singlet-triplet transitions, enhancing understanding of quantum transport.

Contribution

It provides a comprehensive overview of the development of SU(4) Kondo physics and charge fluctuation effects in quantum dot systems with orbital degeneracies.

Findings

SU(4) Kondo effect arises in orbitally degenerate quantum dots.

Charge fluctuations near degeneracy points can be mapped to two-channel Kondo models.

Singlet-triplet transitions significantly influence quantum transport properties.

Abstract

In this lecture note we focus our attention to quantum dot systems where exotic strongly correlated behavior develops due to the presence of orbital or charge degrees of freedom. After giving a concise overview of the theory of transport and Kondo effect through a single electron transistor, we discuss how SU(4) Kondo effect develops in dots having orbitally degenerate states and in double dot systems, and then study the singlet-triplet transition in lateral quantum dots. Charge fluctuations and Matveev's mapping to the two-channel Kondo model in the vicinity of charge degeneracy point are also discussed.