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The link between s and d components of electron boson coupling constants in one band d wave Eliashberg theory for high Tc superconductors
Full text linkThe phenomenology of overdoped high Tc uperconductors can be described by a one band d wave Eliashberg theory where the mechanism of superconducting coupling is mediated by antiferromagnetic spin fl uctuations and whose characteristic energy Ω0 scales with Tc according to the empirical law Ω0 = 5.8 kBTc. This model presents universal characteristics that are independent of the critical temperature such as the link between the s and d components of electron boson coupling constants and the invariance of the ratio 2Δ/kBTc. This situation arises from the particular structure of Eliashberg's equations which, despite being non-linear equations, present solutions with these simple propertie
s±+d wave multiband Eliashberg theory for the iron pnictides
Full text linkWe calculated the critical temperature in the framework of s± + d-wave
multiband Eliashberg theory. We have solved these equations numerically to see
at what values of the input parameters there is a solution with a non-zero critical
temperature and what is the symmetry of the order parameter of this solution. For
our model we consider the pnictide case with simplifications that allow us to obtain
the most general possible information. For selected and representative cases in which
the order parameter has s± + d symmetry, we calculated the superconducting density
of states, the temperature dependence of the gaps, and the superfluid density so that
comparison with experimental data can be made. Finally, we show that such a system
has only a twofold in-plane symmetry and undergoes a transition from nodal to fully
gapped with increasing temperature
Gravitational effects in a superconducting film struck by a laser pulse
Full text linkWe study the local interaction of the gravitational field with a superfluid condensate. To this end, we exploit the Ginzburg–Landau formalism with generalized Maxwell fields. The analysis shows that a slight local alteration of the gravitational field in a thin superconducting film can be achieved by laser pulses with particular characteristics
The critical current of SIS and SIS' high-Tc Josephson junctions with a surface-depressed order parameter
No full textEliashberg equations, pair symmetry and tunnel density of states in the optimally-doped high-Tc superconductor Bi2Sr2CaCu2O8+x
No full textIn this work, in order to compare the theoretical density of states (DOS) to the tunneling data in the optimally-doped high-Tc superconductor (HTS) Bi2Sr2CaCu2O8+x, we calculate the real-axis direct solution of the d-wave equations for the retarded electron-boson interaction in presence of half-filling and impurities. The use of a spectral function containing an isotropic part αs2F(Ω) and an anisotropic one αd2F(Ω) and the simple assumption: αd2F(Ω) = gdαs2F(Ω) where gd is a constant leads, for appropriate values of the isotropic coupling constant λs and the anisotropic one λd, to solutions with only d-wave symmetry for the order parameter Δ(ω) and only s-wave one for the renormalization function Z(ω). The results properly fit both the critical temperature and the DOS in the whole energy range, as recently determined in our break-junction tunneling experiments, but appear unable to do the same in the case of recent STM data
Energy dependence of the normal density of states and of the electron-phonon spectral function in the quasiparticle tunneling of high-Tc superconductors
No full textWe discuss the effects of quasiparticle energy dependence of the normal density of states on the Eliashberg equations in the case of high-Tc superconductors and compare the numerical results with our recent tunneling experimental data in Bi2Sr2CaCu2O8+x with Tc = 93 K. We also consider the possibility of quasiparticle energy dependence of the electron-phonon spectral function α2(Ω)F(Ω) and calculate its effects on the superconducting density of states
Real-axis solution of Eliashberg equations in various order-parameter symmetries and the tunneling conductance of optimally-doped HTCS
No full textIn the present work we calculate the theoretical tunneling conductance curves of SIN junctions involving high-Tc superconductors, for different possible symmetries of the order parameter (s, d, s + id, s + d, anisotropics and extendeds). To do so, we solve the real-axis Eliashberg equations in the case of an half-filled infinite band. We show that some of the peculiar characteristics of HTSC tunneling curves (dip and hump at eV > Δ, broadening of the gap peak, zero bias and so on) can be explained in the framework of the Migdal-Eliashberg theory. The theoretical dI/dV curves calculated for the different symmetries at T=4 K are then compared to various experimental tunneling data obtained in optimally-doped BSCCO, TBCO, HBCO, LSCO and YBCO single crystals. To best fit the experimental data, the scattering by non-magnetic impurities has to be taken into account, thus limiting the sensitivity of this procedure in determining the exact gap symmetry of these materials. Finally, the effect of the temperature on the theoretical tunneling conductance is also discussed and the curves obtained at T = 2 K are compared to those given by the analytical continuation of the imaginary-axis solution
A new NMR facility for solid state actinide research at the Institute for Transuranium Elements
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