717 research outputs found
Vortex State of TlBaCuO via Tl NMR at 2 Tesla
We report a Tl NMR study of vortex state for an aligned
polycrystalline sample of an overdoped high- superconductor
TlBaCuO (85 K) with magnetic field 2 T along
the c axis. We observed an imperfect vortex lattice, so-called Bragg glass at
=5 K, coexistence of vortex solid with liquid between 10 and 60 K, and
vortex melting between 65 and 85 K. No evidence for local antiferromagnetic
ordering at vortex cores was found for our sample.Comment: 4 pages with 5 figure
Phase diagram of heavy fermion systems
The Meccano of heavy fermion systems is shown on different cases going from
anomalous monochalcogenides to cerium intermetallic compounds with special
focus on the ideal case of the CeRu2Si2 series. Discussion is made in the frame
of the interplay between valence, electronic structure (Fermi surface), and
magnetism. The nice tools given by the temperature, the pressure, and the
magnetic field allow to explore different ground states as well as the slow
downhill ''race'' before reaching a Fermi liquid finish line at very low
temperature. Experimentally, the Gr"uneisen parameter i.e. the ratio of the
thermal expansion by the specific heat is a coloured magic number; its
temperature, pressure, and magnetic field dependence is a deep disclosure of
competing hierarchies and the conversion of this adaptive matter to external
responses.Comment: submitted ICM200
KIC 4150611: a rare multi-eclipsing quintuple with a hybrid pulsator
We present the results of our analysis of KIC 4150611 (HD 181469) - an
interesting, bright quintuple system that includes a hybrid
Sct/ Dor pulsator. Four periods of eclipses - 94.2, 8.65, 1.52 and 1.43
d - have been observed by the Kepler satellite, and three point sources (A, B,
and C) are seen in high angular resolution images.
From spectroscopic observations made with the HIDES spectrograph attached to
the 1.88-m telescope of the Okayama Astrophysical Observatory (OAO), for the
first time we calculated radial velocities (RVs) of the component B - a pair of
G-type stars - and combined them with Kepler photometry in order to obtain
absolute physical parameters of this pair. We also managed to directly measure
RVs of the pulsator, also for the first time. Additionally, we modelled the
light curves of the 1.52 and 1.43-day pairs, and measured their eclipse timing
variations (ETVs). We also performed relative astrometry and photometry of
three sources seen on the images taken with the NIRC2 camera of the Keck II
telescope. Finally, we compared our results with theoretical isochrones.
The brightest component Aa is the hybrid pulsator, transited every 94.2 days
by a pair of K/M-type stars (Ab1+Ab2), which themselves form a 1.52-day
eclipsing binary. The components Ba and Bb are late G-type stars, forming
another eclipsing pair with a 8.65 day period. Their masses and radii are
M, R for the
primary, and M, R
for the secondary. The remaining period of 1.43 days is possibly related to a
faint third star C, which itself is most likely a background object. The
system's properties are well-represented by a 35 Myr isochrone. There are also
hints of additional bodies in the system.Comment: 14 pages, 15 figures, 7 tables, to appear in A&A, abstract modified
in order to fit the arXiv limi
A Substellar Companion to the Intermediate-Mass Giant 11 Com
We report the detection of a substellar companion orbiting the
intermediate-mass giant star 11 Com (G8 III). Precise Doppler measurements of
the star from Xinglong station and Okayama Astrophysical Observatory (OAO)
revealed Keplerian velocity variations with an orbital period of 326.03 +/-
0.32 days, a semiamplitude of 302.8 +/- 2.6 m/s, and an eccentricity of 0.231
+/- 0.005. Adopting a stellar mass of 2.7 +/- 0.3 M_solar, the minimum mass of
the companion is 19.4 +/- 1.5 M_Jup, well above the deuterium burning limit,
and the semimajor axis is 1.29 +/- 0.05 AU. This is the first result from the
joint planet search program between China and Japan aiming at revealing
statistics of substellar companions around intermediate-mass giants. 11 Com b
emerged from 300 targets of the planet search program at OAO. The current
detection rate of a brown dwarf candidate seems to be comparable to that around
solar-type stars within orbital separations of 3 AU.Comment: 19 pages, 4 figures, accepted by Ap
Itinerant metamagnetism of CeRu2Si2 : bringing out the dead. Comparison with the new Sr3Ru2O7 case
Focus is given on the macroscopic and microscopic experimental works realized
during a decade on the clear case of itinerant metamagnetism in the heavy
fermion paramagnetic compound CeRu2Si2 . Emphasis is made on the feedback
between the band structure, the exchange coupling and the lattice instability.
Sweeps in magnetic field, pressure and temperature feel the pseudogap of this
strongly correlated electronic system as well as its equivalent CeRu2Ge2 at a
fictitious negative pressure. Some mysteries persist as the complete
observation of the FS above the metamagnetic field HM and the detection of the
dynamical ferromagnetic fluctuation near HM. The novelty of the bilayer
ruthenate Sr3Ru2O7 is discussed by comparison. Despite differences in spin and
electronic dimensionality many common trends emerge.Comment: 14 pages, 9 figure
A Hierarchically-Organized Phase Diagram near a Quantum Critical Point in URu2Si2
A comprehensive transport study, as a function of both temperature and
magnetic field in continuous magnetic fields up to 45 T reveals that URu2Si2
possesses all the essential hallmarks of quantum criticality at temperatures
above 5.5 K and fields around 38 T, but then collapses into multiple low
temperature phases in a hierarchically-organized phase diagram as the
temperature is reduced. Although certain generic features of the phase diagram
are very similar to those in the cuprates and heavy fermion superconductors,
the existence of multiple ordered hysteretic phases near the field-tuned
quantum critical point is presently unique to URu2Si2. This finding suggests
the existence of many competing order parameters separated by small energy
difference in URu2Si2.Comment: 6 pages, twocolum texts, 3 coloured figure included, submitted to PR
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