Quantum phases of correlated electrons in artificial molecules under magnetic fields

Abstract

We investigate the stability of few-electron quantum phases in vertically coupled quantum dots under a magnetic field of arbitrary strength and direction. The orbital and spin stability diagrams of realistic devices containing up to five electrons, from strong to weak inter-dot coupling, is determined. Correlation effects and realistic sample geometries are fully taken into account within the Full Configuration Interaction method. In general, the magnetic field drives the system into a strongly correlated regime by modulating the single-particle gaps. In coupled quantum dots different components of the field, either parallel or perpendicular to the tunneling direction, affect single-dot orbitals and tunneling energy, respectively. Therefore, the stability of the quantum phases is related to different correlation mechanisms, depending on the field direction. Comparison of exact diagonalization results with simple models allows to identify the specific role of correlations.

Controlling spin phases of few electrons in artificial molecules by magnetic fields

“…Nevertheless, we adopt the S/AS terminology to refer to those orbitals, eigenstates of the SP Hamiltonian for any value of B, which continuously evolve from S and AS states as classified at zero field. Note that B affects Coulomb matrix elements only slightly [27], which differs from the case where SAS ∆ is reduced by changing the inter-dot barrier width [18,20].…”

“…[26]. Here we focus on the paradigmatic case of four electrons [27], which is suitable to evidentiate some general trends of ground-state transitions of AMs driven by both in-plane and perpendicular components of B.…”

Isospin phases of vertically coupled double quantum rings under the influence of perpendicular magnetic fields

“…Refs. 17,18,19,20,21,22,23,24,25,26 and references therein. Also, molecular-beam epitaxy techniques have recently allowed the synthesis of quantum ring molecules (QRMs) in the form of concentric double QRs 27,28 and vertically stacked layers of self-assembled QRs, 29,30 the optical and structural properties of the latters having also been characterized by photoluminescence spectroscopy and by atomic force microscopy, respectively.…”