7 research outputs found
Invariance of Charge of Laughlin Quasiparticles
A Quantum Antidot electrometer has been used in the first direct observation
of the fractionally quantized electric charge. In this paper we report
experiments performed on the integer i = 1, 2 and fractional f = 1/3 quantum
Hall plateaus extending over a filling factor range of at least 27%. We find
the charge of the Laughlin quasiparticles to be invariantly e/3, with standard
deviation of 1.2% and absolute accuracy of 4%, independent of filling,
tunneling current, and temperature.Comment: 4 pages, 5 fig
Tunneling images of a 2D electron system in a quantizing magnetic field
We have applied a scanning probe method, Subsurface Charge Accumulation (SCA)
imaging, to resolve the local structure of the interior of a semiconductor
two-dimensional electron system (2DES) in a tunneling geometry. Near magnetic
fields corresponding to integer Landau level filling, submicron scale spatial
structure in the out-of-phase component of the tunneling signal becomes
visible. In the images presented here, the structure repeats itself when the
filling factor is changed from nu=6 to nu=7. Therefore, we believe the images
reflect small modulations in the 2DES density caused by the disorder in the
sample.Comment: 2 pages, 2 color figures, submitted to LT23 proceeding
Edge Dynamics in Quantum Hall Bilayers II: Exact Results with Disorder and Parallel Fields
We study edge dynamics in the presence of interlayer tunneling, parallel
magnetic field, and various types of disorder for two infinite sequences of
quantum Hall states in symmetric bilayers. These sequences begin with the 110
and 331 Halperin states and include their fractional descendants at lower
filling factors; the former is easily realized experimentally while the latter
is a candidate for the experimentally observed quantum Hall state at a total
filling factor of 1/2 in bilayers. We discuss the experimentally interesting
observables that involve just one chiral edge of the sample and the correlation
functions needed for computing them. We present several methods for obtaining
exact results in the presence of interactions and disorder which rely on the
chiral character of the system. Of particular interest are our results on the
331 state which suggest that a time-resolved measurement at the edge can be
used to discriminate between the 331 and Pfaffian scenarios for the observed
quantum Hall state at filling factor 1/2 in realistic double-layer systems.Comment: revtex+epsf; two-up postscript at
http://www.sns.ias.edu/~leonid/ntwoup.p
Magnetic edge states of impenetrable stripe
The electron motion in a strong perpendicular magnetic field close to the
impenetrable stripe is considered by making use of the singular integral
equation technique. The energy spectrum is calculated and compared with the
energy spectrum of the round antidot.Comment: REVTeX4 format, 9 pages with 9 figures (*.eps
Microwave nanobolometer based on proximity Josephson junctions
We introduce a microwave bolometer aimed at high-quantum-efficiency detection of wave packet energy within the framework of circuit quantum electrodynamics, the ultimate goal being single microwave photon detection. We measure the differential thermal conductance between the detector and its heat bath, obtaining values as low as 5fW/K at 50mK. This is one tenth of the thermal conductance quantum and corresponds to a theoretical lower bound on noise-equivalent power of order 10â20W/âHz at 50mK. By measuring the differential thermal conductance of the same bolometer design in substantially different environments and materials, we determine that electron-photon coupling dominates the thermalization of our nanobolometer.Peer reviewe