3,415 research outputs found
Nonequilibrium electron spectroscopy of Luttinger liquids
Understanding the effects of nonequilibrium on strongly interacting quantum
systems is a challenging problem in condensed matter physics. In dimensions
greater than one, interacting electrons can often be understood within
Fermi-liquid theory where low-energy excitations are weakly interacting
quasiparticles. On the contrary, electrons in one dimension are known to form a
strongly-correlated phase of matter called a Luttinger liquid (LL), whose
low-energy excitations are collective density waves, or plasmons, of the
electron gas. Here we show that spectroscopy of locally injected high-energy
electrons can be used to probe energy relaxation in the presence of such strong
correlations. For detection energies near the injection energy, the electron
distribution is described by a power law whose exponent depends in a continuous
way on the Luttinger parameter, and energy relaxation can be attributed to
plasmon emission. For a chiral LL as realized at the edge of a fractional
quantum Hall state, the distribution function grows linearly with the distance
to the injection energy, independent of filling fraction.Comment: 4+ pages, 3 figure
X-ray Development of the Classical Nova V2672 Ophiuchi with Suzaku
We report the Suzaku detection of a rapid flare-like X-ray flux amplification
early in the development of the classical nova V2672 Ophiuchi. Two
target-of-opportunity ~25 ks X-ray observations were made 12 and 22 days after
the outburst. The flux amplification was found in the latter half of day 12.
Time-sliced spectra are characterized by a growing supersoft excess with
edge-like structures and a relatively stable optically-thin thermal component
with Ka emission lines from highly ionized Si. The observed spectral evolution
is consistent with a model that has a time development of circumstellar
absorption, for which we obtain the decline rate of ~10-40 % in a time scale of
0.2 d on day 12. Such a rapid drop of absorption and short-term flux
variability on day 12 suggest inhomogeneous ejecta with dense blobs/holes in
the line of sight. Then on day 22 the fluxes of both supersoft and thin-thermal
plasma components become significantly fainter. Based on the serendipitous
results we discuss the nature of this source in the context of both short- and
long-term X-ray behavior.Comment: To appear in PASJ; 9 pages, 5 figures, 2 table
Magmatic focusing to mid-ocean ridges: the role of grain size variability and non-Newtonian viscosity
Melting beneath mid-ocean ridges occurs over a region that is much broader
than the zone of magmatic emplacement to form the oceanic crust. Magma is
focused into this zone by lateral transport. This focusing has typically been
explained by dynamic pressure gradients associated with corner flow, or by a
sub-lithospheric channel sloping upward toward the ridge axis. Here we discuss
a novel mechanism for magmatic focusing: lateral transport driven by gradients
in compaction pressure within the asthenosphere. These gradients arise from the
co-variation of melting rate and compaction viscosity. The compaction
viscosity, in previous models, was given as a function of melt fraction and
temperature. In contrast, we show that the viscosity variations relevant to
melt focusing arise from grain-size variability and non-Newtonian creep. The
asthenospheric distribution of melt fraction predicted by our models provides
an improved ex- planation of the electrical resistivity structure beneath one
location on the East Pacific Rise. More generally, although grain size and
non-Newtonian viscosity are properties of the solid phase, we find that in the
context of mid-ocean ridges, their effect on melt transport is more profound
than their effect on the mantle corner-flow.Comment: 20 pages, 4 figures, 1 tabl
Virtual turning points and bifurcation of Stokes curves for higher order ordinary differential equations
For a higher order linear ordinary differential operator P, its Stokes curve
bifurcates in general when it hits another turning point of P. This phenomenon
is most neatly understandable by taking into account Stokes curves emanating
from virtual turning points, together with those from ordinary turning points.
This understanding of the bifurcation of a Stokes curve plays an important role
in resolving a paradox recently found in the Noumi-Yamada system, a system of
linear differential equations associated with the fourth Painleve equation.Comment: 7 pages, 4 figure
Detection of highly ionized O and Ne absorption lines in the X-ray spectrum of 4U1820-303 in the globular cluster, NGC 6624
We searched for absorption lines of highly ionized O and Ne in the energy
spectra of two Low-mass X-ray binaries, 4U1820-303 in the globular cluster
NGC6624 and Cyg X-2, observed with the Chandra LETG, and detected O VII, O VIII
and Ne IX absorption lines for 4U1820-303. The equivalent width of the O VII K
alpha line was 1.19 +0.47/-0.30 eV (90 % errors) and the significance was 6.5
sigma. Absorption lines were not detected for Cyg X-2 with a 90 % upper limit
on the equivalent width of 1.06 eV for O VII K alpha. The absorption lines
observed in 4U1820-303 are likely due to hot interstellar medium, because O
will be fully photo-ionized if the absorbing column is located close to the
binary system. The velocity dispersion is restricted to b = 200 - 420 km/s from
consistency between O VII K alpha and K beta lines, Ne/O abundance ratio, and H
column density. The average temperature and the O VII density are respectively
estimated to be log(T[K]) = 6.2 - 6.3 and n(OVII) = (0.7 - 2.3) x 10^{-6}
cm^{-3}. The difference of O VII column densities for the two sources may be
connected to the enhancement of the soft X-ray background (SXB) towards the
Galactic bulge region. Using the polytrope model of hot gas to account for the
SXB we corrected for the density gradient and estimated the midplane O VII
density at the solar neighborhood. The scale height of hot gas is then
estimated using the AGN absorption lines. It is suggested that a significant
portion of both the AGN absorption lines and the high-latitude SXB emission
lines can be explained by the hot gas in our Galaxy.Comment: Accepted for publication in ApJ. 7 pages, 9 eps figure
Molecular transistor coupled to phonons and Luttinger-liquid leads
We study the effects of electron-phonon interactions on the transport
properties of a molecular quantum dot coupled to two Luttinger-liquid leads. In
particular, we investigate the effects on the steady state current and DC noise
characteristics. We consider both equilibrated and unequilibrated on-dot
phonons. The density matrix formalism is applied in the high temperature
approximation and the resulting semi-classical rate equation is numerically
solved for various strengths of electron-electron interactions in the leads and
electron-phonon coupling. The current and the noise are in general smeared out
and suppressed due to intralead electron interaction. On the other hand, the
Fano factor, which measures the noise normalized by the current, is more
enhanced as the intralead interaction becomes stronger. As the electron-phonon
coupling becomes greater than order one, the Fano factor exhibits
super-Poissonian behaviour.Comment: 11 pages, 11 figure
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