15,232 research outputs found
Transport equation for 2D electron liquid under microwave radiation plus magnetic field and the Zero Resistance State
A general transport equation for the center of mass motion is constructed to
study transports of electronic system under uniform magnetic field and
microwave radiation. The equation is applied to study 2D electron system in the
limit of weak disorder where negative resistance instability is observed when
the radiation field is strong enough. A solution of the transport equation with
spontaneous AC current is proposed to explain the experimentally observed
Radiation-Induced Zero Resistance State.Comment: 9 pages, 1 figur
Stabilization of Majorana modes in vortices in the superconducting phase of topological insulators using topologically trivial bands
If superconductivity is induced in the metallic surface states of topological
insulators via proximity, Majorana modes will be trapped on the vortex cores.
The same effects hold for doped topological insulators which become bulk s-wave
superconductors as long as the doping does not exceed a critical values It is this critical chemical potential at which the material
forgets it arose from a band-inverted topological insulator; it loses its
topological \emph{imprint.} For the most common classes of topological
insulators, which can be modeled with a minimal 4-band Dirac model the values
of can be easily calculated, but for materials with more
complicated electronic structures such as HgTe or ScPtBi the result is unknown.
We show that due to the hybridization with an additional Kramers' pair of
topologically trivial bands the topological imprint of HgTe-like electronic
structures (which includes the ternary Heusler compounds) can be widely
extended for p-doping. As a practical consequence we consider the effects of
such hybridization on the range of doping over which Majorana modes will be
bound to vortices in superconducting topological insulators and show that the
range is strongly extended for p-doping, and reduced for n-doping. This leaves
open the possibility that other topological phenomena may be stabilized over a
wider range of doping.Comment: 5 pages, 1 figure, Accepted for publication in Physical Review
Letter
Transverse momentum distribution of vector mesons produced in ultraperipheral relativistic heavy ion collisions
We study the transverse momentum distribution of vector mesons produced in
ultraperipheral relativistic heavy ion collisions (UPCs). In UPCs there is no
strong interaction between the nuclei and the vector mesons are produced in
photon-nucleus collisions where the (quasireal) photon is emitted from the
other nucleus. Exchanging the role of both ions leads to interference effects.
A detailed study of the transverse momentum distribution which is determined by
the transverse momentum of the emitted photon, the production process on the
target and the interference effect is done. We study the total unrestricted
cross section and those, where an additional electromagnetic excitation of one
or both of the ions takes place in addition to the vector meson production, in
the latter case small impact parameters are emphasized.Comment: 12 pages, REVTeX manuscrip
GeV Majorana Neutrinos in Top-quark Decay at the LHC
We explore the \Delta L=2 same-sign dilepton signal from top-quark decay via
a Majorana neutrino at the LHC in the top anti-top pair production samples. The
signature is same-sign dilepton plus multi-jets with no significant missing
energy. The most optimistic region lies where the Majorana neutrino mass is
between 15-65 GeV. For 300 fb^-1 integrated luminosity, it is possible to probe
S_{ij}, the effective mixing parameter, to order of 10^-5.Comment: 15 pages, 8 figure
Biases in metallicity measurements from global galaxy spectra: the effects of flux-weighting and diffuse ionized gas contamination
Galaxy metallicity scaling relations provide a powerful tool for
understanding galaxy evolution, but obtaining unbiased global galaxy gas-phase
oxygen abundances requires proper treatment of the various line-emitting
sources within spectroscopic apertures. We present a model framework that
treats galaxies as ensembles of HII and diffuse ionized gas (DIG) regions of
varying metallicities. These models are based upon empirical relations between
line ratios and electron temperature for HII regions, and DIG strong-line ratio
relations from SDSS-IV MaNGA IFU data. Flux-weighting effects and DIG
contamination can significantly affect properties inferred from global galaxy
spectra, biasing metallicity estimates by more than 0.3 dex in some cases. We
use observationally-motivated inputs to construct a model matched to typical
local star-forming galaxies, and quantify the biases in strong-line ratios,
electron temperatures, and direct-method metallicities as inferred from global
galaxy spectra relative to the median values of the HII region distributions in
each galaxy. We also provide a generalized set of models that can be applied to
individual galaxies or galaxy samples in atypical regions of parameter space.
We use these models to correct for the effects of flux-weighting and DIG
contamination in the local direct-method mass-metallicity and fundamental
metallicity relations, and in the mass-metallicity relation based on
strong-line metallicities. Future photoionization models of galaxy line
emission need to include DIG emission and represent galaxies as ensembles of
emitting regions with varying metallicity, instead of as single HII regions
with effective properties, in order to obtain unbiased estimates of key
underlying physical properties.Comment: 37 pages, 29 figures, 4 tables. Accepted to ApJ. See Figures 15-17
for typical global galaxy biases in strong-line ratios, electron
temperatures, and direct-method metallicitie
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