Symmetry breaking and Wigner molecules in few-electron quantum dots

Abstract

We discuss symmetry breaking in two-dimensional quantum dots resulting from strong interelectron repulsion relative to the zero-point kinetic energy associated with the confining potential. Such symmetry breaking leads to the emergence of crystalline arrangements of electrons in the dot. The so-called Wigner molecules form already at field-free conditions. The appearance of rotating Wigner molecules in circular dots under high magnetic field, and their relation to magic angular momenta and quantum-Hall-effect fractional fillings, is also discussed. Recent calculations for two electrons in an elliptic quantum dot, using exact diagonalization and an approximate generalized-Heitler-London treatment, show that the electrons can localize and form a molecular dimer for screened interelectron repulsion. The calculated singlet-triplet splitting (J) as a function of the magnetic field (B) agrees with cotunneling measurements; its behavior reflects the effective dissociation of the dimer for large B. Knowledge of the dot shape and of J(B) allows determination of two measures of entanglement (concurrence and von Neumann entropy for indistinguishable fermions), whose behavior correlates also with the dissociation of the dimer. The theoretical value for the concurrence at B=0 agrees with the experimental estimates.

LATEX, 12 pages with 6 figures. Invited talk at TNT2005 (Trends in Nanotechnology). To download a file with figures of higher quality, click http://www.prism.gatech.edu/~ph274cy/ (go to publication #74)

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Cited by in corpus (7)

• Symmetry breaking and quantum correlations in finite systems: Studies of quantum dots and ultracold Bose gases and related nuclear and chemical methods
• Symmetry restoration in mean-field approaches
• Incipient Wigner Localization in Circular Quantum Dots
• Rapidly rotating boson molecules with long or short range repulsion: an exact diagonalization study
• Molecular formations and spectra due to electron correlations in three-electron hybrid double-well qubits
• Quantum dots based on parabolic quantum wells: importance of electronic correlations
• The Wigner localization of interacting electrons in a one-dimensional harmonic potential