Phase transitions of a few-electron system in a spherical quantum dot

P. A. Sundqvist, S. Yu. Volkov, Yu. E. Lozovik, and M. Willander
Phys. Rev. B 66, 075335 – Published 29 August 2002
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Abstract

The spin configurations of a spherical quantum dot, defined by a three-dimensional (3D) harmonic confinement potential, containing a few Coulomb Fermi particles (electrons or holes) are studied. Quantum transitions involving a spin transformation and a “cold melting” (from a Wigner crystal-like state, i.e., from regime of strongly correlated electrons, to a Fermi-liquid-like phase) is driven by the dimensionless quantum control parameter q (which is connected with steepness of the confinement potential) is demonstrated. The pair correlation and radial distribution functions which characterize electronic quantum delocalization are analyzed. The calculations using the unrestricted variational Hartree-Fock method (for the ground state at T=0K) and the more computer intensive quantum path integral Monte Carlo method (for T0K) are performed and compared. For small q, the ground state of the three electron system is crystal-like and has C3 symmetry, i.e., the maxima of electron density are located at the nodes of an equilateral triangle. The preferable spin configuration for small q is “ferromagnetic,” with total spin S=3/2. As q rises, the widths of the one-electron wave functions grow and become overlapping. At a critical value q1 the ground state changes from S=3/2 to S=1/2 and at the same time, asymmetry appears in the triangle (i.e., spontaneous breaking of the C3 symmetry to C2 symmetry). At a second critical value q2 the electron distribution undergoes a symmetry phase transition, from trianglelike (with C2 symmetry) to axial symmetric (with C symmetry). As q grows further, we obtain a Fermi-liquid-like (non-interacting) electron configuration in the ground state (S=1/2). In addition, the S=3/2 state, at a critical q value (which is slightly larger than q1) undergoes a dramatic charge redistribution.

  • Received 26 December 2001

DOI:https://doi.org/10.1103/PhysRevB.66.075335

©2002 American Physical Society

Authors & Affiliations

P. A. Sundqvist1,*, S. Yu. Volkov2, Yu. E. Lozovik2, and M. Willander1

  • 1Laboratory of Physical Electronics and Photonics, MC2, Department of Physics, University of Gothenburg and Chalmers University of Technology, Fysikgränd 3, S-412 96 Gothenburg, Sweden
  • 2Institute of Spectroscopy, 142190 Moscow Region, Troitsk, Russia

  • *Email address: sunkan@fy.chalmers.se

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Issue

Vol. 66, Iss. 7 — 15 August 2002

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