5 research outputs found
Unified description of floppy and rigid rotating Wigner molecules formed in quantum dots
Restoration of broken circular symmetry is used to explore the
characteristics of the ground states and the excitation spectra of rotating
Wigner molecules (RWM's) formed in two-dimensional parabolic N-electron quantum
dots. In high magnetic fields, the RWM's are floppy rotors with the energies of
the magic angular momentum (L) states obeying aL + b/L^{1/2}. Under such fields
the ground-state energies (referenced to the kinetic energy in the lowest
Landau level) approach the electrostatic energy of N point charges in the
classical equilibrium molecular configuration. At zero field and strong
interelectron repulsion, the RWM's behave like quasiclassical rigid rotors
whose energies vary as L^2. The particular L-dependence in high B is inherent
and natural to a floppy rotating WM, and it can be used as a crucial diagnostic
tool for resolving the recently posed question whether the composite-fermion or
the RWM picture is appropriate for QD's.Comment: 5 pages. Revtex4 with 3 EPS figures and 2 tables . For related
papers, see http://www.prism.gatech.edu/~ph274c
Quantifying the levitation picture of extended states in lattice models
The behavior of extended states is quantitatively analyzed for two
dimensional lattice models. A levitation picture is established for both
white-noise and correlated disorder potentials. In a continuum limit window of
the lattice models we find simple quantitative expressions for the extended
states levitation, suggesting an underlying universal behavior. On the other
hand, these results point out that the Quantum Hall phase diagrams may be
disorder dependent.Comment: 5 pages, submitted to PR
Sequential magnetotunneling in a vertical quantum dot tuned at the crossing to higher spin states
We have calculated the Linear magnetoconductance across a vertical parabolic quantum dot with a magnetic field in the direction of the current. Gate voltage and magnetic field an tuned at the degeneracy point between the occupancies N=2 and N=3, close to the singlet-triplet transition for N=2. We find that the conductance is enhanced prior to the transition by nearby crossings of the levels of the three-particle dot. Immediately after it is depressed by roughly 1/3, as long as the total spin S of the three-electron ground state doesn't change from S=1/2 to S=3/2, due to spin selection rule. At low temperature this dip is very sharp, but the peak is recovered by increasing the temperature