235 research outputs found
Magnetization of noncircular quantum dots
We calculate the magnetization of quantum dots deviating from circular
symmetry for noninteracting electrons or electrons interacting according to the
Hartree approximation. For few electrons the magnetization is found to depend
on their number, and the shape of the dot. The magnetization is an ideal probe
into the many-electron state of a quantum dot.Comment: 11 RevTeX pages with 6 included Postscript figure
Magnetoplasmons in quantum rings
We have studied the structure and dipole charge density response of nanorings
as a function of the magnetic field using local-spin density functional theory.
Two small rings consisting of 12 and 22 electrons confined by a positively
charged background are used to represent the cases of a narrow and a wide ring.
The results are qualitatively compared with experimental data existing on
microrings and on antidots. A smaller ring containing 5 electrons is also
analyzed to allow for a closer comparison with a recent experiment on a two
electron quantum ring.Comment: Typeset using Revtex, 13 pages and 11 Postscript figure
High Magnetic Field Microwave Conductivity of 2D Electrons in an Array of Antidots
We measure the high magnetic field () microwave conductivity,
Re, of a high mobility 2D electron system containing an antidot
array. Re vs frequency () increases strongly in the regime of
the fractional quantum Hall effect series, with Landau filling .
At microwave , Re vs exhibits a broad peak centered around
. On the peak, the 10 GHz Re can exceed its dc-limit
value by a factor of 5. This enhanced microwave conductivity is unobservable
for temperature K, and grows more pronounced as is
decreased. The effect may be due to excitations supported by the antidot edges,
but different from the well-known edge magnetoplasmons.Comment: 4 pages, 3 figures, revtex
Plasmon Modes and Correlation Functions in Quantum Wires and Hall Bars
We present microscopic derivations of the one-dimensional low-energy boson
effective Hamiltonians of quantum wire and quantum Hall bar systems. The
quantum Hall system is distinguished by its spatial separation of oppositely
directed electrons. We discuss qualitative differences in the plasmon
collective mode dispersions and the ground state correlation functions of the
two systems which are consequences of this difference. The slowly-decaying
quasi-solid correlations expected in a quantum wire are strongly suppressed in
quantum Hall bar systems.Comment: 7 pages, RevTex, 3 figures and 1 table included; references updated
and minor typos correcte
Electronic Spectral Functions for Quantum Hall Edge States
We have evaluated wavevector-dependent electronic spectral functions for
integer and fractional quantum Hall edge states using a chiral Luttinger liquid
model. The spectral functions have a finite width and a complicated line shape
because of the long-range of the Coulomb interaction. We discuss the
possibility of probing these line shapes in vertical tunneling experiments.Comment: 4 pages, RevTex, two figures included, to appear as a Rapid
Communication in PRB; we updated references which have recently appeared in
print and were cited as preprints in our ealier submissio
Far-infrared edge modes in quantum dots
We have investigated edge modes of different multipolarity sustained by
quantum dots submitted to external magnetic fields. We present a microscopic
description based on a variational solution of the equation of motion for any
axially symmetric confining potential and multipole mode. Numerical results for
dots with different number of electrons whose ground-state is described within
a local Current Density Functional Theory are discussed. Two sum rules, which
are exact within this theory, are derived. In the limit of a large neutral dot
at B=0, we have shown that the classical hydrodynamic dispersion law for edge
waves \omega(q) \sim \sqrt{q \ln (q_0/q)} holds when quantum and finite size
effects are taken into account.Comment: We have changed some figures as well as a part of the tex
Far-infrared edge modes in quantum dots
We have investigated edge modes of different multipolarity sustained by
quantum dots submitted to external magnetic fields. We present a microscopic
description based on a variational solution of the equation of motion for any
axially symmetric confining potential and multipole mode. Numerical results for
dots with different number of electrons whose ground-state is described within
a local Current Density Functional Theory are discussed. Two sum rules, which
are exact within this theory, are derived. In the limit of a large neutral dot
at B=0, we have shown that the classical hydrodynamic dispersion law for edge
waves \omega(q) \sim \sqrt{q \ln (q_0/q)} holds when quantum and finite size
effects are taken into account.Comment: We have changed some figures as well as a part of the tex
Current Density Functional approach to large quantum dots in intense magnetic fields
Within Current Density Functional Theory, we have studied a quantum dot made
of 210 electrons confined in a disk geometry. The ground state of this large
dot exhibits some features as a function of the magnetic field (B) that can be
attributed in a clear way to the formation of compressible and incompressible
states of the system. The orbital and spin angular momenta, the total energy,
ionization and electron chemical potentials of the ground state, as well as the
frequencies of far-infrared edge modes are calculated as a function of B, and
compared with available experimental and theoretical results.Comment: Typeset using Revtex, 17 pages and 13 Postscript figure
Edge-Magnetoplasmon Wave-Packet Revivals in the Quantum Hall Effect
The quantum Hall effect is necessarily accompanied by low-energy excitations
localized at the edge of a two-dimensional electron system. For the case of
electrons interacting via the long-range Coulomb interaction, these excitations
are edge magnetoplasmons. We address the time evolution of localized
edge-magnetoplasmon wave packets. On short times the wave packets move along
the edge with classical E cross B drift. We show that on longer times the wave
packets can have properties similar to those of the Rydberg wave packets that
are produced in atoms using short-pulsed lasers. In particular, we show that
edge-magnetoplasmon wave packets can exhibit periodic revivals in which a
dispersed wave packet reassembles into a localized one. We propose the study of
edge-magnetoplasmon wave packets as a tool to investigate dynamical properties
of integer and fractional quantum-Hall edges. Various scenarios are discussed
for preparing the initial wave packet and for detecting it at a later time. We
comment on the importance of magnetoplasmon-phonon coupling and on quantum and
thermal fluctuations.Comment: 18 pages, RevTex, 7 figures and 2 tables included, Fig. 5 was
originally 3Mbyte and had to be bitmapped for submission to archive; in the
process it acquired distracting artifacts, to upload the better version, see
http://physics.indiana.edu/~uli/publ/projects.htm
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