7,274 research outputs found
Effects of particle-number conservation on heat capacity of nuclei
By applying the particle-number projection to the finite-temperature BCS
theory, the -shaped heat capacity, which has recently been claimed to be a
fingerprint of the superfluid-to-normal phase transition in nuclei, is
reexamined. It is found that the particle-number (or number-parity) projection
gives -shapes in the heat capacity of nuclei which look qualitatively
similar to the observed ones. These -shapes are accounted for as effects of
the particle-number conservation on the quasiparticle excitations, and occur
even when we keep the superfluidity at all temperatures by assuming a constant
gap in the BCS theory. The present study illustrates significance of the
conservation laws in studying phase transitions of finite systems.Comment: RevTeX4, 12 pages including 5 figures (1 color figure), to be
published in PR
Evolution from Non-Fermi to Fermi Liquid Transport Properties by Isovalent Doping in BaFe2(As1-xPx)2 Superconductors
The normal-state charge transport is studied systematically in high-quality
single crystals of BaFe(AsP) (). By
substituting isovalent P for As, the spin-density-wave (SDW) state is
suppressed and the dome-shaped superconducting phase ( K)
appears. Near the SDW end point (), we observe striking linear
temperature () dependence of resistivity in a wide -range, and remarkable
low- enhancement of Hall coefficient magnitude from the carrier number
estimates. We also find that the magnetoresistance apparently violates the
Kohler's rule and is well scaled by the Hall angle as
. These non-Fermi liquid
transport anomalies cannot be attributed to the simple multiband effects. These
results capture universal features of correlated electron systems in the
presence of strong antiferromagnetic fluctuations.Comment: 4 pages, 4 figure
New Bardeen-Cooper-Schrieffer-type theory at finite temperature with particle-number conservation
We formulate a new Bardeen-Cooper-Schrieffer (BCS)-type theory at finite
temperature, by deriving a set of variational equations of the free energy
after the particle-number projection. With its broad applicability, this theory
can be a useful tool for investigating the pairing phase transition in finite
systems with the particle-number conservation. This theory provides effects of
the symmetry-restoring fluctuation (SRF) for the pairing phenomena in finite
fermionic systems, distinctively from those of additional quantum fluctuations.
It is shown by numerical calculations that the phase transition is compatible
with the conservation in this theory, and that the SRF shifts up the critical
temperature (). This shift of occurs due to
reduction of degrees-of-freedom in canonical ensembles, and decreases only
slowly as the particle-number increases (or as the level spacing narrows), in
contrast to the conventional BCS theory.Comment: 10 pages including 3 figures, to be published in Phys. Rev.
Properties of Recurrent Nova T Pyxidis Based on 2011 Outburst
We reexamine the properties of the recurrent nova T Pyxidis based on our own spectroscopic data accompanying with the photometric ones by VSOLJ (Variable Star Observers League in Japan) during 2011 outburst. One of the purpose of this paper is whether a missing outburst could be happen around 1988-1989. Comparing the 2011 outburst data with previous ones, we may conclude that any essential difference can not be found. Accordingly it is difficult to deny a small possibility of a ”missing” outburst from 1988 to 1989, taking into account the seasonal gap in its observation for northern hemisphere observers . The problem whether IM Normae belongs to be a member of T Pyx subclass or not is to be postponed by its next outburst taking into account of T Pyx’s peculiar spectral behavior
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