74 research outputs found
An Anderson-Fano Resonance and Shake-Up Processes in the Magneto-Photoluminescence of a Two-Dimensional Electron System
We report an anomalous doublet structure and low-energy satellite in the
magneto-photoluminescence spectra of a two-dimensional electron system. The
doublet structure moves to higher energy with increasing magnetic field and is
most prominent at odd filling factors 5 and 3. The lower-energy satellite peak
tunes to lower energy for increasing magnetic field between filling factor 6
and 2. These features occur at energies below the fundamental band of
recombination originating from the lowest Landau level and display striking
magnetic field and temperature dependence that indicates a many-body origin.
Drawing on a recent theoretical description of Hawrylak and Potemski, we show
that distinct mechanisms are responsible for each feature.Comment: 14 pages including 5 figures. To appear in the April 15th edition of
Phy. Rev. B. rapid com
Skyrmionic excitons
We investigate the properties of a Skyrmionic exciton consisting of a
negatively charged Skyrmion bound to a mobile valence hole. A variational wave
function is constructed which has the generalized total momentum P as a good
quantum number. It is shown that the Skyrmionic exciton can have a larger
binding energy than an ordinary magnetoexciton and should therefore dominate
the photoluminescence spectrum in high-mobility quantum wells and
heterojunctions where the electron-hole separation exceeds a critical value.
The dispersion relation for the Skyrmionic exciton is discussed.Comment: 9 pages, RevTex, 2 PostScript figures. Replaced with version to
appear in Phys. Rev. B Rapid Communications. Short discussion of variational
state adde
Tunneling Between a Pair of Parallel Hall Droplets
In this paper, we examine interwell tunneling between a pair of fractional
quantum Hall liquids in a double quantum well system in a tilted magnetic
field. Using a variational Monte Carlo method, we calculate moments of the
intra-Landau level tunneling spectrum as a function of in-plane field component
and interwell spacing . This is done for variety of
incompressible states including a pair of layers ([330]), pair of
layers ([550]), and Halperin's [331] state. The results suggest a
technique to extract interwell correlations from the tunneling spectral data.Comment: 21 pages and 8 figures (included), RevTeX, preprint no. UCSDCU
Theory of anyon excitons: Relation to excitons of nu=1/3 and nu=2/3 incompressible liquids
Elementary excitations of incompressible quantum liquids (IQL's) are anyons,
i.e., quasiparticles carrying fractional charges and obeying fractional
statistics. To find out how the properties of these quasiparticles manifest
themselves in the optical spectra, we have developed the anyon exciton model
(AEM) and compared the results with the finite-size data for excitons of nu=1/3
and nu=2/3 IQL's. The model considers an exciton as a neutral composite
consisting of three quasielectrons and a single hole. The AEM works well when
the separation between electron and hole confinement planes, h, is larger than
the magnetic length l. In the framework of the AEM an exciton possesses
momentum k and two internal quantum numbers, one of which can be chosen as the
angular momentum, L, of the k=0 state. Existence of the internal degrees of
freedom results in the multiple branch energy spectrum, crater-like electron
density shape and 120 degrees density correlations for k=0 excitons, and the
splitting of the electron shell into bunches for non-zero k excitons. For h
larger than 2l the bottom states obey the superselection rule L=3m (m are
integers starting from 2), all of them are hard core states. For h nearly 2l
there is one-to-one correspondence between the low-energy spectra found for the
AEM and the many- electron exciton spectra of the nu=2/3 IQL, whereas some
states are absent from the many-electron spectra of the nu=1/3 IQL. We argue
that this striking difference in the spectra originates from the different
populational statistics of the quasielectrons of charge conjugate IQL's and
show that the proper account of the statistical requirements eliminates
excessive states from the spectrum. Apparently, this phenomenon is the first
manifestation of the exclusion statistics in the anyon bound states.Comment: 26 pages with 9 figures, typos correcte
Energy spectra of fractional quantum Hall systems in the presence of a valence hole
The energy spectrum of a two-dimensional electron gas (2DEG) in the
fractional quantum Hall regime interacting with an optically injected valence
band hole is studied as a function of the filling factor and the
separation between the electron and hole layers. The response of the 2DEG
to the hole changes abruptly at of the order of the magnetic length
. At , the hole binds electrons to form neutral () or
charged () excitons, and the photoluminescence (PL) spectrum probes the
lifetimes and binding energies of these states rather than the original
correlations of the 2DEG. The ``dressed exciton'' picture (in which the
interaction between an exciton and the 2DEG was proposed to merely enhance the
exciton mass) is questioned. Instead, the low energy states are explained in
terms of Laughlin correlations between the constituent fermions (electrons and
's) and the formation of two-component incompressible fluid states in the
electron--hole plasma. At , the hole binds up to two Laughlin
quasielectrons (QE) of the 2DEG to form fractionally charged excitons
QE. The previously found ``anyon exciton'' QE is shown to be
unstable at any value of . The critical dependence of the stability of
different QE complexes on the presence of QE's in the 2DEG leads to the
observed discontinuity of the PL spectrum at or .Comment: 16 pages, 14 figures, submitted to PR
- …