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91.
C. Camerlingo H. Huang B. Ruggiero M. Russo E. Sarnelli G. Testa 《Il Nuovo Cimento D》1994,16(12):1967-1972
Summary Bicrystal grain boundary junctions of YBCO have been fabricated by using the Inverted Cylindrical Magnetron d.c. sputtering
technique. The main characteristics of the junction behaviour are reported. Some aspects of the experimental results are discussed
in the framework of existing models developed for describing weak-link structures.
Paper presented at the ?VII Congresso SATT?, Torino, 4–7 October 1994. 相似文献
92.
W.H. Wong C.F. Lo 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,6(2):213-223
In the present work we have developed an optimal coupled-cluster approximation, which can take care of both the accuracies
of the ground-state energy and the wavefunction estimates, for the ground state of a two-state system coupled to a dispersionless
boson bath. This new approach is also able to give a tight upper bound to the ground-state energy of the system. Up to the
fourth level of this approximation our results show excellent agreement with the numerical exact diagonalization results.
In particular, our results suggest no discontinuous localization-delocalization transition of the two-state system. This is
consistent with the exact result.
Received: 11 March 1998 / Accepted: 23 June 1998 相似文献
93.
The I-V characteristics of a Josephson junction shunted by an Ohmic resistor shows sharp peaks when levels in neighbouring wells are crossing. We consider the shape and size of these peaks using a double-well model where the wells are given in parabolic approximation. The friction of arbitrary strength is included by the help of a bath of infinitely many degrees of freedom. 74.50.+z. 相似文献
94.
Summary In an important experiment performed on a SQUID system, Rouse, Han and Lukens report the first observation of resonant tunnelling
between macroscopically distinct quantum levels. We support the experiment with the first theoretical approach for the phenomenon. 相似文献
95.
G. Tonini F. Werner Y. Castin 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,39(2):283-294
We investigate theoretically the formation of a vortex lattice in
a superfluid two-spin component Fermi gas in a rotating harmonic trap, in a BCS-type
regime of condensed non-bosonic pairs.
Our analytical solution of the superfluid
hydrodynamic equations, both for the 2D BCS equation of state
and for the 3D unitary quantum gas, predicts that the vortex free gas is
subject to a dynamic instability for fast enough rotation.
With a numerical solution of the full
time dependent BCS equations in a 2D model, we confirm the existence of this dynamic
instability and we show that it leads to the formation of a regular pattern
of quantum vortices in the gas. 相似文献
96.
K. P. Schmidt A. Reischl G. S. Uhrig 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,38(2):343-352
In this work we give a consistent picture of the thermodynamic properties of
bosons in the Mott insulating phase when loaded adiabatically into
one-dimensional optical lattices. We find a crucial dependence of the
temperature in the optical lattice on the doping level of the Mott
insulator. In the undoped case, the temperature is of the order of the large
onsite
Hubbard interaction. In contrast, at a finite doping level the
temperature jumps almost immediately to the order of the small hopping
parameter. These two situations are investigated on the one hand by considering
limiting cases like the atomic limit and the case of free fermions. On the
other hand, they are examined using a quasi-particle conserving continuous
unitary transformation extended by an approximate thermodynamics for
hardcore particles. 相似文献
97.
E. Lundh 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,46(3):517-520
Two effects are identified that affect the visibility of the
Mott transition in an atomic gas in an optical lattice confined
in a power-law potential. The transition can be made more
pronounced by increasing the power law, but at the same time,
experimental uncertainty in the number of particles will
induce corresponding fluctuations in the measured condensate
fraction. Calculations in two dimensions
indicate that a potential slightly more flat-bottomed than a
quadratic one is to be preferred for a wide range of
particle number fluctuation size. 相似文献
98.
99.
Summary Man-made low-dimensional magnetic systems including surfaces, interfaces and multilayers, have attracted a great amount of
attention in the past decade because, as expected, the lowered symmetry and coordination number offer a variety of opportunities
for inducing new and exotic phenomena and so hold out the promise of new device applications. Local spin density functional
(LSDF)ab initio electronic-structure calculations employing the full-potential-linearized augmented-plane-wave (FLAPW) method have played
a key role in the development of this exciting field by not only providing a clearer understanding of the experimental observations
but also predicting new systems with desired properties. One of the striking successes of theory in the last decade has been
the calculation of hyperfine fields at surfaces and interfaces. Concurrently, several groups have followed the pioneering
work of Korecki and Gradmann and have measured hyperfine fields at surfaces and interfaces. In this paper, we review new features
of hyperfine-interaction investigations in man-made materials which emphasizes how the close interplay of theoretical determinations
and experiment are essential because the hyperfine field is not proportional to the magnetization and so interpretations of
experiment are totally dependent on theory.
Paper presented at ICAME-95, Rimini, 10–16 September 1995. 相似文献
100.
Summary We study the effect of temperature on the lifetime of the resonant macroscopic quantum tunnelling voltage state. In view of
experiments we consider a merit factor in order to balance between measuring extremely small signals of longer duration or
larger signals of shorter duration. 相似文献