Intermediate Low Spin States in a Few-electron Quantum Dot in the ν ≤ 1 Regime

Applied Geophysics and Petrophysics, Delft University of Technology, Delft, South Holland, Netherlands
Physical Review B (Impact Factor: 3.74). 12/2005; 74(3). DOI: 10.1103/PhysRevB.74.033306
Source: arXiv


We study the effects of electron-electron interactions in a circular few-electron vertical quantum dot in such a strong magnetic field that the filling factor $\nu\le 1$. We measure excitation spectra and find ground state transitions beyond the maximum density droplet ($\nu=1$) region. We compare the observed spectra with those calculated by exact diagonalization to identify the ground state quantum numbers, and find that intermediate low-spin states occur between adjacent spin-polarized magic number states. Comment: 4 pages, 4 figures

  • [Show abstract] [Hide abstract]
    ABSTRACT: The ability of the hyperfine interaction to lift spin blockade was studied for vertically coupled double quantum dots in two different regimes of potential detuning between the two dots. The double dot has a triplet state, which is a sufficiently long-lived excited state to block current flow by the Pauli effect. This blockade is lifted by a spin flip transition to the singlet state, generating a leakage current. The singlet-triplet separation or exchange energy decreases with increasing detuning. For small detuning, the leakage current shows a step when the Zeeman energy equals the exchange energy thus turning on the flip-flop interaction. The threshold magnetic field gradually increases with decreasing detuning. It increases more abruptly near the resonance of two singlet states reflecting the increased exchange energy. For large detuning, the leakage current is caused by singlet-triplet mixing due to the fluctuating nuclear field, and it decreases when the Zeeman energy exceeds the fluctuating nuclear field energy. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
    No preview · Article · Nov 2006 · physica status solidi (b)
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Intermediate spin states that occur in electrostatic dots in the magnetic field regime just beyond the maximum density droplet are investigated. The 5-electron system is studied with exact diagonalization and group theory. The results indicate that the intermediate spin states are mixed symmetry states with a superposition of 5- and 4-fold electron-molecule configurations. A superposition of 5- and 4-fold correlation functions is found to reproduce the exact mixed symmetry pair correlation function to around 2%.
    Preview · Article · Dec 2006 · physica status solidi (c)
  • [Show abstract] [Hide abstract]
    ABSTRACT: Triplet-singlet spin relaxation in a vertical electrostatic quantum dot containing two interacting electrons is studied with a realistic model that includes the effects of finite thickness and screening. The spin relaxation mechanism is taken to be spin mixing via the part of the Dresselhaus Hamiltonian that is linear in the lateral momentum. The electron-electron interaction enhances relaxation and finite thickness suppresses it. The relaxation rate varies extremely rapidly with well width, w, approximately like 1∕w18 in zero magnetic field and 1∕w10 in a nonzero magnetic field. In addition, the rate oscillates with w and this leads to further suppression of relaxation. If w is sufficiently large the linear spin mixing mechanism is suppressed to the extent that it is no longer dominant.
    No preview · Article · Jan 2007 · Physical review. B, Condensed matter
Show more