Interactions and Interference in Quantum Dots: Kinks in Coulomb Blockade Peak Positions

TL;DR

This paper explores how quantum interference and electron interactions in quantum dots cause unexpected spin states and conductance kinks, providing insights into exchange energies in chaotic electron systems.

Contribution

It demonstrates that electron interactions can induce spin-triplet ground states in quantum dots, leading to conductance kinks, challenging the shell-structure expectation.

Findings

Accidental spin-triplet ground states occur even with weak interactions.

External parameters can switch the ground state, causing conductance kinks.

Experimental observation of kinks can measure exchange energy.

Abstract

We investigate the spin of the ground state of a geometrically confined many-electron system. For atoms, shell structure simplifies this problem-- the spin is prescribed by the well-known Hund's rule. In contrast, quantum dots provide a controllable setting for studying the interplay of quantum interference and electron-electron interactions in general cases. In a generic confining potential, the shell-structure argument suggests a singlet ground state for an even number of electrons. The interaction among the electrons produces, however, accidental occurrences of spin-triplet ground states, even for weak interaction, a limit which we analyze explicitly. Variaton of an external parameter causes sudden switching between these states and hence a kink in the conductance. Experimental study of these kinks would yield the exchange energy for the ``chaotic electron gas''.