3,381 research outputs found
Itinerant chiral ferromagnetism in a trapped Rashba spin-orbit coupled Fermi gas
How ferromagnetic phases emerge in itinerant systems is an outstanding
problem in quantum magnetism. Here we consider a repulsive two-component Fermi
gas confined in a two dimensional isotropic harmonic potential and subject to a
large Rashba spin-orbit (SO) coupling, whose single-particle dispersion can be
tailored by adjusting the SO coupling strength. We show that the interplay
among SO coupling, correlation effects and mean-field repulsion leads to a
competition between ferromagnetic and non-magnetic phases. At intermediate
interaction strengths, ferromagnetic phase emerges which can be well described
by the mean-field Hartree-Fock theory; whereas at strong interaction strengths,
a strongly correlated non-magnetic phase is favored due to the
beyond-mean-field quantum correlation effects. Furthermore, the ferromagnetic
phase of this system possesses a chiral current density induced by the Rashba
spin-orbit coupling, whose experimental signature is investigated.Comment: Main text: 5 pages, 6 figures; Supplement: 4 pages, 2 figure
A Method for Neuronal Source Identification
Multi-sensor microelectrodes for extracellular action potential recording
have significantly improved the quality of in vivo recorded neuronal signals.
These microelectrodes have also been instrumental in the localization of
neuronal signal sources. However, existing neuron localization methods have
been mostly utilized in vivo, where the true neuron location remains unknown.
Therefore, these methods could not be experimentally validated. This article
presents experimental validation of a method capable of estimating both the
location and intensity of an electrical signal source. A four-sensor
microelectrode (tetrode) immersed in a saline solution was used to record
stimulus patterns at multiple intensity levels generated by a stimulating
electrode. The location of the tetrode was varied with respect to the
stimulator. The location and intensity of the stimulator were estimated using
the Multiple Signal Classification (MUSIC) algorithm, and the results were
quantified by comparison to the true values. The localization results, with an
accuracy and precision of ~ 10 microns, and ~ 11 microns respectively, imply
that MUSIC can resolve individual neuronal sources. Similarly, source intensity
estimations indicate that this approach can track changes in signal amplitude
over time. Together, these results suggest that MUSIC can be used to
characterize neuronal signal sources in vivo.Comment: 14 pages, 5 figure
Exposure of the Hidden Anti-Ferromagnetism in Paramagnetic CdSe:Mn Nanocrystals
We present theoretical and experimental investigations of the magnetism of
paramagnetic semiconductor CdSe:Mn nanocrystals and propose an efficient
approach to the exposure and analysis of the underlying anti-ferromagnetic
interactions between magnetic ions therein. A key advance made here is the
build-up of an analysis method with the exploitation of group theory technique
that allows us to distinguish the anti-ferromagnetic interactions between
aggregative Mn2+ ions from the overall pronounced paramagnetism of magnetic ion
doped semiconductor nanocrystals. By using the method, we clearly reveal and
identify the signatures of anti-ferromagnetism from the measured temperature
dependent magnetisms, and furthermore determine the average number of Mn2+ ions
and the fraction of aggregative ones in the measured CdSe:Mn nanocrystals.Comment: 26 pages, 5 figure
- …