15,223 research outputs found
Phonon emission and arrival times of electrons from a single-electron source
In recent charge-pump experiments, single electrons are injected into quantum Hall edge channels at energies significantly above the Fermi level. We consider here the relaxation of these hot edge-channel electrons through longitudinal-optical-phonon emission. Our results show that the probability for an electron in the outermost edge channel to emit one or more phonons en route to a detector some microns distant along the edge channel suffers a double-exponential suppression with increasing magnetic field. This explains recent experimental observations. We also describe how the shape of the arrival-time distribution of electrons at the detector reflects the velocities of the electronic states post phonon emission. We show how this can give rise to pronounced oscillations in the arrival-time-distribution width as a function of magnetic field or electron energy
Field-driven topological glass transition in a model flux line lattice
We show that the flux line lattice in a model layered HTSC becomes unstable
above a critical magnetic field with respect to a plastic deformation via
penetration of pairs of point-like disclination defects. The instability is
characterized by the competition between the elastic and the pinning energies
and is essentially assisted by softening of the lattice induced by a
dimensional crossover of the fluctuations as field increases. We confirm
through a computer simulation that this indeed may lead to a phase transition
from crystalline order at low fields to a topologically disordered phase at
higher fields. We propose that this mechanism provides a model of the low
temperature field--driven disordering transition observed in neutron
diffraction experiments on single crystals.Comment: 11 pages, 4 figures available upon request via snail mail from
[email protected]
Nonmetallic Low-Temperature Normal State of K0.70Fe1.46Se1.85Te0.15
The normal-state in-plane resistivity below the zero-field superconducting
transition temperature and the upper critical field Hc2 were measured by
suppressing superconductivity in pulsed magnetic fields for
K0.70Fe1.46Se1.85Te0.15. The normal-state resistivity is found to
increase logarithmically with decrasing temperature as
. Similar to granular metals, our results suggest
that a superconductor - insulator transition below zero-field T may be
induced in high magnetic fields. This is related to the intrinsic real-space
phase-separated states common to all inhomogeneous superconductors.Comment: 6 pages, 4 figure
Observation of persistent flow of a Bose-Einstein condensate in a toroidal trap
We have observed the persistent flow of Bose-condensed atoms in a toroidal
trap. The flow persists without decay for up to 10 s, limited only by
experimental factors such as drift and trap lifetime. The quantized rotation
was initiated by transferring one unit, , of the orbital angular
momentum from Laguerre-Gaussian photons to each atom. Stable flow was only
possible when the trap was multiply-connected, and was observed with a BEC
fraction as small as 15%. We also created flow with two units of angular
momentum, and observed its splitting into two singly-charged vortices when the
trap geometry was changed from multiply- to simply-connected.Comment: 1 file, 5 figure
- …