18 research outputs found
Multiple Scattering of Fractionally-Charged Quasiparticles
We employ shot noise measurements to characterize the effective charge of
quasiparticles, at filling factor nu=1/3 of the fractional quantum Hall regime,
as they scatter from an array of identical weak backscatterers. Upon
scattering, quasiparticles are known to bunch, e.g., only three e/3 charges, or
'electrons' are found to traverse a rather opaque potential barrier. We find
here that the effective charge scattered by an array of scatterers is
determined by the scattering strength of an individual scatterer and not by the
combined scattering strength of the array, which can be very small. Moreover,
we also rule out intra-edge equilibration of e/3 quasiparticles over length
scale of hundreds microns.Comment: 4 pages, 4 figure
Shot-noise spectroscopy of energy-resolved ballistic currents
We investigate the shot noise of nonequilibrium carriers injected into a
ballistic conductor and interacting via long-range Coulomb forces. Coulomb
interactions are shown to act as an energy analyzer of the profile of injected
electrons by means of the fluctuations of the potential barrier at the emitter
contact. We show that the details in the energy profile can be extracted from
shot-noise measurements in the Coulomb interaction regime, but cannot be
obtained from time-averaged quantities or shot-noise measurements in the
absence of interactions.Comment: 7 pages, 4 figure
Evidence for non-linear quasiparticle tunneling between fractional quantum Hall edges
Remarkable nonlinearities in the differential tunneling conductance between
fractional quantum Hall edge states at a constriction are observed in the
weak-backscattering regime. In the = 1/3 state a peak develops as
temperature is increased and its width is determined by the fractional charge.
In the range this width displays a symmetric behavior
around = 1/2. We discuss the consistency of these results with available
theoretical predictions for inter-edge quasiparticle tunneling in the
weak-backscattering regime
The Evolution of Quasiparticle Charge in the Fractional Quantum Hall Regime
The charge of quasiparticles in a fractional quantum Hall (FQH) liquid,
tunneling through a partly reflecting constriction with transmission t, was
determined via shot noise measurements. In the nu=1/3 FQH state, a charge
smoothly evolving from e*=e/3 for t=1 to e*=e for t<<1 was determined, agreeing
with chiral Luttinger liquid theory. In the nu=2/5 FQH state the quasiparticle
charge evolves smoothly from e*=e/5 at t=1 to a maximum charge less than e*=e/3
at t<<1. Thus it appears that quasiparticles with an approximate charge e/5
pass a barrier they see as almost opaque.Comment: 4 pages, Correct figure 3 and caption include
Fractional Quantum Hall States of Clustered Composite Fermions
The energy spectra and wavefunctions of up to 14 interacting quasielectrons
(QE's) in the Laughlin nu=1/3 fractional quantum Hall (FQH) state are
investigated using exact numerical diagonalization. It is shown that at
sufficiently high density the QE's form pairs or larger clusters. This
behavior, opposite to Laughlin correlations, invalidates the (sometimes
invoked) reapplication of the composite fermion picture to the individual QE's.
The series of finite-size incompressible ground states are identified at the QE
filling factors nu_QE=1/2, 1/3, 2/3, corresponding to the electron fillings
nu=3/8, 4/11, 5/13. The equivalent quasihole (QH) states occur at nu_QH=1/4,
1/5, 2/7, corresponding to nu=3/10, 4/13, 5/17. All these six novel FQH states
were recently discovered experimentally. Detailed analysis indicates that QE or
QH correlations in these states are different from those of well-known FQH
electron states (e.g., Laughlin or Moore-Read states), leaving the origin of
their incompressibility uncertain. Halperin's idea of Laughlin states of QP
pairs is also explored, but is does not seem adequate.Comment: 14 pages, 9 figures; revision: 1 new figure, some new references,
some new data, title chang
Challenges in the adjuvant chemotherapy of a patient with colorectal cancer with impaired drug metabolism due to multiple single nucleotide polymorphisms (SNPs).
Bunching of fractionally charged quasiparticles tunnelling through high-potential barriers
dSarm/Sarm1 is required for activation of an injury-induced axon death pathway
Axonal and synaptic degeneration is a hallmark of peripheral neuropathy, brain injury, and neurodegenerative disease. Axonal degeneration has been proposed to be mediated by an active autodestruction program, akin to apoptotic cell death; however, loss-of-function mutations capable of potently blocking axon self-destruction have not been described. Here, we show that loss of the Drosophila Toll receptor adaptor dSarm (sterile alpha/Armadillo/Toll-Interleukin receptor homology domain protein) cell-autonomously suppresses Wallerian degeneration for weeks after axotomy. Severed mouse Sarm1 null axons exhibit remarkable long-term survival both in vivo and in vitro, indicating that Sarm1 prodegenerative signaling is conserved in mammals. Our results provide direct evidence that axons actively promote their own destruction after injury and identify dSarm/Sarm1 as a member of an ancient axon death signaling pathway