Impurity effects in few-electron quantum dots: Incipient Wigner molecule regime

Abstract

Numerically exact path-integral Monte Carlo data are presented for $N\le 10$ strongly interacting electrons confined in a 2D parabolic quantum dot, including a defect to break rotational symmetry. Low densities are studied, where an incipient Wigner molecule forms. A single impurity is found to cause drastic effects: (1) The standard shell-filling sequence with magic numbers $N=4,6,9$, corresponding to peaks in the addition energy $\Delta (N)$, is destroyed, with a new peak at N=8, (2) spin gaps decrease, (3) for N=8, sub-Hund's rule spin S=0 is induced, and (4) spatial ordering of the electrons becomes rather sensitive to spin. We also comment on the recently observed bunching phenomenon.

arXiv comment7 pages, 1 table, 4 figures, accepted for publication in Europhysics Letters

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• Path-integral Monte Carlo simulations for interacting few-electron quantum dots with spin-orbit coupling
• Transport properties of quantum dots in the Wigner molecule regime
• Re-entrant pinning of Wigner molecules in a magnetic field due to a Coulomb impurity
• The Crossover between Liquid and Solid Electron Phases in Quantum Dots: A Large-Scale Configuration-Interaction Study
• Electron correlation in metal clusters, quantum dots and quantum rings
• Solving fermion problems without solving the sign problem: symmetry-breaking wave functions from similarity-transformed propagators for solving 2D quantum dots
• Determinant- and Derivative-Free Quantum Monte Carlo Within the Stochastic Representation of Wavefunctions
• Magnetic-field-induced binding of few-electron systems in shallow quantum dots
• Path-integral Monte Carlo study of electronic states in quantum dots in an external magnetic field