Collective Excitations in Double Quantum Dots

TL;DR

This paper investigates the collective excitations and spin order in double quantum dots at filling factor 2, revealing potential links to decoherence in qubit systems through specific excitation modes.

Contribution

It provides a detailed analysis of collective excitations and spin ordering in double quantum dots, highlighting new excitation modes and their possible role in decoherence.

Findings

Identification of roton-like minima indicating order within the ground state

Demonstration of spin order in canted and symmetric states

Proposal that certain excitations may cause decoherence in qubit systems

Abstract

We analyse the ground state properties of vertical double quantum dots in the lowest Landau level regime for filling factor \nu=2. This analysis follow two lines: on the one hand, we study the dispersion relation of different collective excitations and look for the roton-type minima that signal some type of order within the ground state. On the other hand, we calculate expected values of the antiferremagnetic order operator defined as <S_x^RS_x^L>. We conclude that of the three existing types of ground state at \nu=2 the canted and symmetric states show spin order on the plane of the dots. In the case of the canted state, two types of spin order are shown as a consequence of the coupling between spin and isospin. We propose that one of the excitations obtained over the symmetric state could be the origin of one of the decoherent processes detected experimentally in qubit sysytems.