0000000000150464
AUTHOR
Bernhard Kramer
showing 5 related works from this author
Magnetic field dependence of quantum dot ground states
2008
We study the ground states of a planar quantum dot with N = 5,6,7 electrons, in the presence of a perpendicular magnetic field. Using a spatially unrestricted Hartree Fock technique followed by spin and angular momentum symmetry restoration, chemical potentials are calculated and transitions between different ground states are identified. A spin blockade in the 6 -> 7 transition is found. The structure of the quantum dot wave functions is illustrated by their electron densities. (c) 2007 Elsevier B.V. All rights reserved.
Transport properties of quantum dots in the Wigner molecule regime
2009
The transport properties of quantum dots with up to N=7 electrons ranging from the weak to the strong interacting regime are investigated via the projected Hartree-Fock technique. As interactions increase radial order develops in the dot, with the formation of ring and centered-ring structures. Subsequently, angular correlations appear, signalling the formation of a Wigner molecule state. We show striking signatures of the emergence of Wigner molecules, detected in transport. In the linear regime, conductance is exponentially suppressed as the interaction strength grows. A further suppression is observed when centered-ring structures develop, or peculiar spin textures appear. In the nonline…
Spin projected unrestricted Hartree-Fock ground states for harmonic quantum dots
2008
We report results for the ground state energies and wave functions obtained by projecting spatially unrestricted Hartree Fock states to eigenstates of the total spin and the angular momentum for harmonic quantum dots with $N\leq 12$ interacting electrons including a magnetic field states with the correct spatial and spin symmetries have lower energies than those obtained by the unrestricted method. The chemical potential as a function of a perpendicular magnetic field is obtained. Signature of an intrinsic spin blockade effect is found.
Spin and rotational symmetries in unrestricted Hartree–Fock states of quantum dots
2007
Ground state energies are obtained using the unrestricted Hartree Fock method for up to four interacting electrons parabolically confined in a quantum dot subject to a magnetic field. Restoring spin and rotational symmetries we recover Hund first rule. With increasing magnetic field, crossovers between ground states with different quantum numbers are found for fixed electron number that are not reproduced by the unrestricted Hartree Fock approximation. These are consistent with the ones obtained with more refined techniques. We confirm the presence of a spin blockade due to a spin mismatch in the ground states of three and four electrons.
Quantum fluctuations of the conductance in the hopping regime
1992
Abstract The results of the numerical scaling approach for localization are used to discuss the statistical behaviour of the zero-temperature conductance of disordered systems of finite size. In the asymptotic regime of strong localization, where transport is dominated by hopping processes, explicit expressions for the temperature dependence of the fluctuations of the conductance and the resistance are obtained by assuming that the phase coherence length is given by the Mott hopping law. It is shown that the temperature dependence of the fluctuations of the logarithm of the conductance/resistance does not depend on the assumptions concerning the statistics of the hopping processes. The resu…