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81.
Verlinde recently developed a theoretical account of gravitation in terms of an entropic force. The central element in Verlinde’s derivation is information and its relation with entropy through the holographic principle. The application of this approach to the case of superconductors requires to take into account that information associated with superconductor’s quantum vacuum energy is not stored on Planck size surface elements, but in four volume cells with Planck-Einstein size. This has profound consequences on the type of gravitational force generated by the quantum vacuum condensate in superconductors, which is closely related with the cosmological repulsive acceleration responsible for the accelerated expansion of the Universe. Remarkably this new gravitational type force depends on the level of breaking of the weak equivalence principle for cooper pairs in a given superconducting material, which was previously derived by the author starting from similar principles. It is also shown that this new gravitational force can be interpreted as a surface force. The experimental detection of this new repulsive gravitational-type force appears to be challenging. 相似文献
82.
L. Benfatto S. Caprara C. Di Castro 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,17(1):95-102
We describe the spectral properties of underdoped cuprates as resulting from a momentum-dependent pseudogap in the normal-state
spectrum. Such a model accounts, within a BCS approach, for the doping dependence of the critical temperature and for the
two-parameter leading-edge shift observed in the cuprates. By introducing a phenomenological temperature dependence of the
pseudogap, which finds a natural interpretation within the stripe quantum-critical-point scenario for high- superconductors, we reproduce also the bifurcation near optimum doping. Finally, we briefly discuss the different role of the gap and the pseudogap in determining
the spectral and thermodynamical properties of the model at low temperatures.
Received 17 February 2000 相似文献
83.
We study the electrical transport properties of a quantum point contact between a lead and a high Tc superconductor. For this, we use the Hamiltonian approach and non-equilibrium Green functions of the system. The electrical current and the shot noise are calculated with this formalism. We consider dx2−y2, dxy, dx2−y2+is and dxy+is symmetries for the pair potential. Also we explore the s+− and s++ symmetries describing the behavior of the ferropnictides superconductors. We found that for dxy symmetry there is not a zero bias conductance peak and for d+is symmetries there is a displacement of the transport properties. From shot noise and current, the Fano factor is calculated and we found that it takes values of effective charge between e and 2e , this is explained by the diffraction of quasiparticles in the contact. For the s+− and s++ symmetries the results show that the electrical current and the shot noise depend on the mixing coefficient, furthermore, the effective electric charge can take values between 0 and 2e, in contrast with the results obtained for s wave superconductors. 相似文献
84.
Motonari Suzuki Masahiko Hayashi Hiromichi Ebisawa 《Journal of Physics and Chemistry of Solids》2008,69(12):3253-3256
We study the dynamics of phase differences in intrinsic Josephson junctions by using numerical simulations. We especially pay attention to the dynamics of junctions with weak dissipation under an externally applied electric current, where nonlinear character of the system appears most significant. It is found that, when an electric current is applied, the spatially localized oscillations appear. These oscillations are similar to the so-called “breather modes”, which are well known in the dynamics of the sine-Gordon systems. We show that the development of these modes depends on the number of junctions, and the dynamics significantly differs between even and odd numbers. As a result, the critical current of the system also undergoes this even-odd effect. 相似文献
85.
Mo Mu 《计算数学(英文版)》2001,(4)
1. IntroductionDomain decomposition methods have undergone great development in the past decade andthere has been rich mathematical theory for model problems. It is worthy to examine how theSemethods can be effectively applied to predical problems where the model problem analysis doesnot trivially apply. It is far from of~ng that there remains not much new for domain decomposition theoretically and Practically. In terms of domain partition, domain decompositionmethods are claSsiced as twO ir… 相似文献
86.
P. Singha Deo V. A. Schweigert F. M. Peeters A. K. Geim 《Physica E: Low-dimensional Systems and Nanostructures》1998,1(1-4)
The Ginzburg–Landau equations coupled with the three-dimensional Maxwell equations are solved for the disc geometry in order to explain recent magnetization experiments. In order to explain the experimental results on a 0.5
m radius Al disc, we have to assume that the superconducting state stays in the lowest angular momentum giant-vortex state even in regions where it is not the lowest energy state. 相似文献
87.
Andrew P Iyengar Ying-Jer KaoQijin Chen K Levin 《Journal of Physics and Chemistry of Solids》2002,63(12):2349-2351
We demonstrate that the observed dependences of Tc and T∗ on small magnetic fields can be readily understood in a precursor superconductivity approach to the pseudogap phase. In this approach, the presence of a pseudogap at Tc (but not at T∗) and the associated suppression of the density of states lead to very different sensitivities to pair-breaking perturbations for the two temperatures. Our semi-quantitative results address the puzzling experimental observation that the coherence length ξ is weakly dependent on hole concentration x throughout most of the phase diagram. We present our results in a form which can be compared with the recent experiments of Shibauchi et al. and argue that orbital effects contribute in an important way to the H dependence of T∗. 相似文献
88.
F. Venturini M. OpelR. Hackl H. BergerL. Forró B. Revaz 《Journal of Physics and Chemistry of Solids》2002,63(12):2345-2348
We report electronic Raman scattering measurements on Bi2Sr2(Y1−xCax)Cu2O8+δ single crystals at different doping levels. The dependence of the spectra on doping and on incoming photon energy is analyzed for different polarization geometries, in the superconducting and in the normal state. We find the scaling behavior of the superconductivity pair-breaking peak with the carrier concentration to be very different in B1g and B2g geometries. Also, we do not find evidence of any significant variation in the lineshape of the spectra in the overdoped region in both symmetries, while we observe a reduction of the intensity in B2g upon decreasing photon energies. The normal state data are analyzed in terms of the memory-function approach. The quasiparticle relaxation rates in the two symmetries display a dependence on energy and temperature which varies with the doping level. 相似文献
89.
Mototada Kobayashi Nozomu Kimata Satoshi Heguri 《Journal of Physics and Chemistry of Solids》2010,71(4):689-691
The X-ray diffraction (XRD), magnetic susceptibility and electron spin resonance (ESR) measurements have been carried out for NaxC60. The XRD profiles with x<4 can be assigned to a face-centered cubic (fcc) lattice, while those with 4≦x to a hexagonal one. The temperature dependence of magnetic susceptibility χ for NaxC60 using SQUID was fitted to the Curie law, and estimated temperature-independent component χ0. The composition x dependence of the χ0 for NaxC60 shows two maxima at around x=3 and x=10, and minimum at x=6. The absence of Pauli contribution at x=6 was confirmed using ESR. A trace of superconducting transition at 14 K has been found for some NaxC60 specimens with 8<x<9. 相似文献
90.