共查询到7条相似文献,搜索用时 0 毫秒
1.
Yunkyu Bang 《Physica C: Superconductivity and its Applications》1999,320(3-4):233-238
Assuming a phenomenological self-energy ImΣ(ω)|ω|β, (β=1), which becomes gapped below Tc, we derived a new gap equation. The new gap equation contains the effect of the kinetic energy gain upon developing a superconducting order parameter. However, this new kinetic energy gain mechanism works only for a repulsive pairing potential leading to a s-wave state. In this case, compared to the usual potential energy gain in the superconducting state as in the BCS gap equation, the kinetic energy gain is more effective to easily achieve a high critical temperature Tc, since it is naturally Fermi energy scale. In view of the experimental evidences of a d-wave pairing state in the hole-doped copper-oxide high-Tc superconductors, we discuss the implications of our results. 相似文献
2.
A.M. Strydom 《Physica B: Condensed Matter》2009,404(19):2981-2984
A first report of physical properties of the ternary intermetallic compound CeRu2Al10 is given. The electrical resistivity below room temperature shows activated behaviour with a narrow gap of before the onset of a sharp peak in ρ(T) below . The Hall coefficient as well as the thermoelectric power are overall positive, and both increase in a similarly sharp manner below T*. The lattice part of the thermal conductivity indicates phonon coupling of the heat transport at T*, possibly underlying a lattice transformation that accompanies the putative metal-to-insulator and magnetic phase transitions. 相似文献
3.
S. Pal S. Hébert C. Yaicle C. Martin A. Maignan 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,53(1):5-9
We report on the resistivity (ρ), thermoelectric power (S for Seebeck)
and magnetic measurements of the series Pr1-xCaxCrO3
(x=0.0–0.5). These orthochromites exhibit a T independent, large and
positive S, from 100 K to 700 K which follows the Cr4+ concentration.
Upon Ca2+ for Pr3+ substitution, a concomitant decrease of the
resistivity and S values is found. The evolution of S as a function of hole
concentration (Cr4+) can be nicely fitted by the modified Heikes
formula which takes into account the orbital degeneracy associated to
Cr3+/Cr4+. This is in good agreement with the model previously
calculated by Marsh and Parris, in the case of weak magnetic coupling [Phys.
Rev. B 54, 7720 (1996)]. The magnetic susceptibility measurements support
the assumption of a weak magnetic coupling since the antiferromagnetic
ordering TN values are found to be lower than 250 K. For
Pr0.7Ca0.3CrO3, the power factor PF= S2/ρ
measured at 700 K is equal to 1.9×10-4 W m-1K-2. The present
system, chemically stable in air up to T > 1000 °C, is promising for
thermoelectric application at very high temperature. 相似文献
4.
S. C. Bradley R. Bulla A. C. Hewson G -M. Zhang 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,11(4):535-550
The O(3) symmetric Anderson model is an example of a system which has a stable low energy marginal Fermi liquid fixed point
for a certain choice of parameters. It is also exactly equivalent, in the large U limit, to a localized model which describes the spin degrees of freedom of the linear dispersion two channel Kondo model.
We first use an argument based on conformal field theory to establish this precise equivalence with the two channel model.
We then use the numerical renormalization group (NRG) approach to calculate both one-electron and two-electron response functions
for a range of values of the interaction strength U. We compare the behaviours about the marginal Fermi liquid and Fermi liquid fixed points and interpret the results in terms
of a renormalized Majorana fermion picture of the elementary excitations. In the marginal Fermi liquid case the spectral densities
of all the Majorana fermion modes display a dependence on the lowest energy scale, and in addition the zero Majorana mode has a delta function contribution. The weight
of this delta function is studied as a function of the interaction U and is found to decrease exponentially with U for large U. Using the equivalence with the two channel Kondo model in the large U limit, we deduce the dynamical spin susceptibility of the two channel Kondo model over the full frequency range. We use renormalized
perturbation theory to interpret the results and to calculate the coefficient of the ln divergence found in the low frequency behaviour of the T=0 dynamic susceptibility.
Received 29 January 1999 相似文献
5.
K.-V. Pham M. Gabay P. Lederer 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,9(4):573-576
Standard bosonization techniques lead to phonon-like excitations in a Luttinger liquid (LL), reflecting the absence of Landau
quasiparticles in these systems. Yet in addition to the above excitations some LL are known to possess solitonic states carrying
fractional quantum numbers (e.g. the spin 1/2 Heisenberg chain). We have reconsidered the zero modes in the low-energy spectrum of the Gaussian boson LL Hamiltonian
both for fermionic and bosonic LL: in the spinless case we find that two elementary excitations carrying fractional quantum
numbers allow to generate all the charge and current excited states of the LL. We explicitly compute the wavefunctions of
these two objects and show that one of them can be identified with the 1D version of the Laughlin quasiparticle introduced
in the context of the Fractional Quantum Hall effect. For bosons, the other quasiparticle corresponds to a spinon excitation.
The eigenfunctions of Wen's chiral LL Hamiltonian are also derived: they are quite simply the one dimensional restrictions
of the 2D bulk Laughlin wavefunctions.
Received 26 January 1999 and Received in final form 21 April 1999 相似文献
6.
M.B. Zölfl Th. Maier Th. Pruschke J. Keller 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,13(1):47-53
We study one-particle spectra and the electronic band-structure of a CuO
2
-plane within the three-band Hubbard model. The Dynamical Mean-Field Theory (DMFT) is used to solve the many particle problem.
The calculations show that the optical gap is given by excitations from the lower Hubbard band into the so called Zhang-Rice singlet band. The optical gap turns out to be considerably smaller than the bare charge transfer energy () for a typical set of parameters, which is in agreement with experiment. We also investigate the dependence of the shape
of the Fermi surface on the different hopping parameters t
CuO and t
OO. A value t
OO
/
t
CuO
>0 leads to a Fermi surface surrounding the M point.
Received 21 September 1998 and Received in final form 8 June 1999 相似文献
7.
Michael Caffrey Joshua Kaufman Stephen J. Stahl Paul T. Wingfield Angela M. Gronenborn G.Marius Clore 《Journal of magnetic resonance (San Diego, Calif. : 1997)》1998,135(2):368-372
A suite of 3D NMR experiments for measuring15N–{1H} NOE,15NT1, and15NT1ρvalues in large proteins, uniformly labeled with15N and13C, is presented. These experiments are designed for proteins that exhibit extensive spectral overlap in the 2D1H–15N HSQC spectrum. The pulse sequences are readily applicable to perdeuterated samples, which increases the spectral resolution and signal-to-noise ratio, thereby permitting the characterization of protein dynamics to be extended to larger protein systems. Application of the pulse sequences is demonstrated on a perdeuterated13C/15N-labeled sample of the 44 kDa ectodomain of SIV gp41. 相似文献