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1.
Starting from a model of free Fermions in two dimensions with an arbitrary strong effective interaction, we derive a Ginzburg-Landau theory describing the crossover from BCS-superconductivity to Bose-condensation. We find a smooth crossover from the standard BCS-limit to a Gross-Pitaevski type equation for the order parameter in a Bose superfluid. The mean field transition temperature exhibits a maximum at a coupling strength, where the behaviour crosses over from BCS to Bose like with corresponding values of 2 Δ0/Tc ≈ 5 which are characteristic for high Tc superconductors. 相似文献
2.
V.G. Molinari M. Sumini F. Rocchi 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,12(2):211-217
The study of quantum degenerate gases has received much interest in these last years essentially thanks to the extremely important
experimental results of the achievement of Bose-Einstein condensation of atoms and, very recently, of almost complete degeneracy
of atomic fermion gases. Here we want to present the results of a semi-analytical method for the study of an interacting degenerate
fermion gas based on semiclassical kinetic theory; special care has been devoted to the study of a rotating electron gas,
in a cylindrically symmetrical configuration, radially confined by a uniform magnetic field. The model will lead to a particular
Thomas-Fermi equation which is generalized to take into account finite temperature and average velocity of the gas, and which
is further developed to consider the effects of external fields.
Received 10 March 2000 相似文献
3.
4.
Amitava Datta 《Pramana》1993,40(6):L503-L509
It is argued with the help of an illustrative model, that the inter species hierarchy among the fermion masses and the quark
mixing angles can be accommodated naturally in the standard model with (approximate) flavor democracy provided there are three
exactly massless neutrinos and four families of sequential quark-leptons with all members of the fourth family having roughly
equal masses. The special problem of light neutrino masses (if any) and possible solutions are also discussed. 相似文献
5.
Nicola Bellomo Nils Calander Eugen Mamontov Magnus Willander 《Comptes Rendus Mecanique》2003,331(7):461-467
6.
Among heavy-fermion (HF) superconductors, CeCoIn 5 exhibits a record high value of T c =2.3 K at ambient pressure [1]. CeCoIn 5 belongs to a new class of HF-superconductors that crystallize in the tetragonal HoCoGa 5 -structure. This structure can be regarded as alternating layers of CeIn 3 and CoIn 2 . Bulk CeIn 3 undergoes a transition from an antiferromagnetic (AFM) state at ambient pressure ( T N =10.2 K) to a superconducting state with very low T C =0.15 K at a critical pressure p c =2.8 GPa [2] at which long range magnetic order vanishes. It is, therefore, regarded as a possible candidate for magnetically mediated superconductivity (SC). We report on measurements of the heat capacity of CeCoIn 5 at hydrostatic pressures p h 1.5 GPa. While T c increases with increasing pressure, the effective mass of the quasi-particles m eff decreases, as indicated by the ratio C / T | T c . As a working hypothesis based on theories of a nearly antiferromagnetic Fermi-liquid (NAFFL), this may be interpreted as the stabilization of the superconducting state by an increase of the characteristic spin fluctuation temperature T_{SF} (T_{SF}\propto k_F^2/m_{\rm eff}). 相似文献
7.
M. Hinczewski A. N. Berker 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,51(4):461-472
The anisotropic d=3 tJ model is studied by
renormalization-group theory, yielding the evolution of the system
as interplane coupling is varied from the isotropic
three-dimensional to quasi-two-dimensional regimes.
Finite-temperature phase diagrams, chemical potential shifts, and
in-plane and interplane kinetic energies and antiferromagnetic
correlations are calculated for the entire range of electron
densities. We find that the novel τ phase, seen in earlier
studies of the isotropic d=3 tJ model, persists even for
strong anisotropy. While the τ phase appears at low
temperatures at 30–35% hole doping away from 〈
ni〉=1, at smaller hole dopings we see a complex lamellar
structure of antiferromagnetic and disordered regions, with a
suppressed chemical potential shift, a possible marker of
incommensurate ordering in the form of microscopic stripes. An
investigation of the renormalization-group flows for the isotropic
two-dimensional tJ model also shows a clear pre-signature of the
τ phase, which in fact appears with finite transition
temperatures upon addition of the smallest interplane coupling. 相似文献
8.
Sambhu N. Datta 《Journal of Chemical Sciences》2007,119(5):351-356
The retarded interaction between an electron and a spin-0 nucleus, that has been derived from electro-dynamical perturbation
theory is discussed here. A brief account of the derivation is given. The retarded form is correct through order v
2/c
2. Use of the relative coordinates leads to an effective one-electron operator that can be used through all orders of perturbation
theory. A few unitary transformations give rise to the interaction that is valid in the non-relativistic limit. 相似文献
9.
X. X. Yi 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,39(3):465-469
For both cases with and without interactions, bipartite
entanglement of two fermions from a Fermi gas in a trap is
investigated. We show how the entanglement depends on the
locations of the two fermions and the total particle number of the
Fermi gas. Fermions at the edge of trap have longer entanglement
distance (beyond it, the entanglement disappears) than those in
the center. We derive a lower limitation to the average
overlapping for two entangled fermions in the BCS ground state,
it is shown to be
, a function of Cooper pair number
Q and the total number of occupied energy levels M. 相似文献
10.
W. Wonneberger 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,48(2):241-253
The phase theory of two interacting one-dimensional degenerate Fermi gases confined to different harmonic traps is developed
based on the concept of bosonization. The excitation spectra of mass and composition waves are calculated and stability boundaries
as function of interaction strength and frequency detuning of the traps are found. The experimentally accessible non-local
mobilities and their relation to the excitation frequencies are also studied. The problem of
the Kohn mode within phase theory is discussed and a solution is proposed. As an example of
the simplicity and effectiveness of the new approach the propagation of a composition
perturbation across the Fermi seas is calculated analytically. 相似文献