Abstract:Sintered powders of SmBa2Cu3O7-x have been prepared and characterized. The physical properties, superconducting temperature transition, up to 92 K, magnetic susceptibility, electrical resistivity and thermopower have been studied as a function of the preparation conditions and therefore of oxygen stoichiometry. The upper critical field has been estimated from resistivity measurements in fields up to 8 T and the slope (dBc2/dT)Tc found to be close to 4 TK-1 for the highest Tc samples. Studies of the electrical … Show more
“…1 Even though the pressure derivative of T c for PrBa 2 Cu 3 O y with T c ϭ85 K(dT c /dP ϭ3.5 K/GPa) is almost an order of magnitude higher than that of optimally doped YBa 2 Cu 3 O 7Ϫ␦ , this value is comparable to 4.0 K/GPa in the underdoped YBa 2 Cu 3 O 6.78 with T c Ӎ87.6 K. 8 Interestingly, the underdoped SmBa 2 Cu 3 O 7Ϫ␦ sample with T c ϭ78 K possesses the same dT c /dP ϭ3.5 K/GPa. 51 These results strongly indicate that the unusual large value of dT c /dP in superconducting PrBa 2 Cu 3 O y possibly comes from the underdoped nature.…”
Section: Origin Of Unusually Large T C Enhancement In Prba 2 Cu 3 mentioning
The pressure dependence of the superconducting transition temperature T c in RBa 2 Cu 3 O 7Ϫ␦ (RϭY and rare earths͒ series has been investigated systematically on the basis of the t-tЈ-tЉ-J model with d-wave pairing by taking into account the variations of the hole concentration in the CuO 2 planes and the effective interaction with pressure. It is shown that the pressure-induced change of hole concentration increases with the trivalent rare-earth ion radius. The calculated T c and its pressure derivative dT c /dP are found to be the increasing functions of the radius of the R 3ϩ ions for the fully oxygenated RBa 2 Cu 3 O 7 . Good agreement with experiments suggests that the rare-earth ion size effect on dT c /dP in RBa 2 Cu 3 O 7 mainly originates from the pressure-induced charge transfer from the charge reservoir CuO chain to the conducting CuO 2 planes. The change of dT c /dP with hole concentration and the pressure dependence of T c in the recently discovered superconducting PrBa 2 Cu 3 O y are well reproduced in this simple model. We have arrived at the conclusion that the unusually large T c enhancement in PrBa 2 Cu 3 O y under pressure results from its underdoped nature. Further experiments are proposed to enhance T c at ambient pressure in PrBa 2 Cu 3 O y .
“…1 Even though the pressure derivative of T c for PrBa 2 Cu 3 O y with T c ϭ85 K(dT c /dP ϭ3.5 K/GPa) is almost an order of magnitude higher than that of optimally doped YBa 2 Cu 3 O 7Ϫ␦ , this value is comparable to 4.0 K/GPa in the underdoped YBa 2 Cu 3 O 6.78 with T c Ӎ87.6 K. 8 Interestingly, the underdoped SmBa 2 Cu 3 O 7Ϫ␦ sample with T c ϭ78 K possesses the same dT c /dP ϭ3.5 K/GPa. 51 These results strongly indicate that the unusual large value of dT c /dP in superconducting PrBa 2 Cu 3 O y possibly comes from the underdoped nature.…”
Section: Origin Of Unusually Large T C Enhancement In Prba 2 Cu 3 mentioning
The pressure dependence of the superconducting transition temperature T c in RBa 2 Cu 3 O 7Ϫ␦ (RϭY and rare earths͒ series has been investigated systematically on the basis of the t-tЈ-tЉ-J model with d-wave pairing by taking into account the variations of the hole concentration in the CuO 2 planes and the effective interaction with pressure. It is shown that the pressure-induced change of hole concentration increases with the trivalent rare-earth ion radius. The calculated T c and its pressure derivative dT c /dP are found to be the increasing functions of the radius of the R 3ϩ ions for the fully oxygenated RBa 2 Cu 3 O 7 . Good agreement with experiments suggests that the rare-earth ion size effect on dT c /dP in RBa 2 Cu 3 O 7 mainly originates from the pressure-induced charge transfer from the charge reservoir CuO chain to the conducting CuO 2 planes. The change of dT c /dP with hole concentration and the pressure dependence of T c in the recently discovered superconducting PrBa 2 Cu 3 O y are well reproduced in this simple model. We have arrived at the conclusion that the unusually large T c enhancement in PrBa 2 Cu 3 O y under pressure results from its underdoped nature. Further experiments are proposed to enhance T c at ambient pressure in PrBa 2 Cu 3 O y .
“…Some other superconductors reveal their high pressure properties in the region of small α (of the order of 0.1 or 1). Examples of such systems include: niobium, zinc, tin, and SmBaCuO 38 , where for the latter one T c = 78.5 K at p = 0, T c = 86.3 K at p = 2 GPa, x 0 = 1 and χ = −1.05 for which and . All of them are type-(D) materials.…”
Section: Effects Of External Hydrostatic Pressurementioning
confidence: 99%
“…42 .Figure 5Critical temperature vs. pressure for selected superconductors: NaCoO, SmBaCuO, TlBaCuO, NdFeAsOF, YBaCuO. Black filled circles (●) indicate the experimental data according to refs 34–38 , respectively.…”
Section: Effects Of External Hydrostatic Pressurementioning
A simplified analytical model of the effect of high pressure on the critical temperature and other thermodynamic properties of superconducting systems is developed using the general conformal transformation method and group-theoretical arguments. Relationships between the characteristic ratios and and the stability of the superconducting state is discussed. Including a single two-parameter fluctuation in the density of states, placed away from the Fermi level, stable solutions determined by are found. It is shown that the critical temperature Tc(p), as a function of high external pressure, can be predicted from experimental data, based on the values of the two characteristic ratios, the critical temperature, and a pressure coefficient measured at zero pressure. The model can be applied to s-wave low-temperature and high-temperature superconductors, as well as to some novel superconducting systems of the new generation. The problem of emergence of superconductivity under high pressure is explained as well. The discussion is illustrated by using experimental data for superconducting elements available in the literature. A criterion for compatibility of experimental data is formulated, allowing one to identify incompatible measurement data for superconducting systems for which the maximum or the minimum critical temperature is achieved under high pressure.
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