共查询到20条相似文献,搜索用时 15 毫秒
1.
I. N. Askerzade 《JETP Letters》2005,81(11):583-586
The temperature dependence of the anisotropy parameter of the upper critical field \(\gamma _{H_{c2} } (T) = H_{c2}^\parallel (T)/H_{c2}^ \bot (T)\) is calculated using the two-band Ginzburg-Landau theory for layered superconductors. It is shown that the anisotropy parameter γ(T) increases with decreasing temperature. The results of the calculations are in agreement with experimental data for single crystals of MgB2 and with other calculations. 相似文献
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I.N. Askerzade B. Tanatar 《理论物理通讯》2009,51(3):563-569
The temperature dependence of the anisotropy parameter of upper critical field γHc2(T)=H_{c2}||(T)/H_{c2}^{\bot}(T) and London penetration depth γλ(T)=λ_{\perp} (T)/λ_{\bot} (T) are calculated using two-band Ginzburg-Landau theory for layered superconductors. It is shown that, with decreasing temperature the anisotropy parameter γ_{H_{c2}}(T) is increased, while theLondon penetration depth anisotropy γλ(T) reveals n opposite behavior.Results of our calculations are in agreement with experimental datafor single crystal MgB2 nd with other calculations. Results of an analysis of magnetic field Hc1 in a single vortex between superconducting layers are also presented. 相似文献
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An analytical formula is obtained for the temperature dependence of the anisotropy parameter of the upper critical field of a two-band superconductor in the context of the generalized Ginzburg-Landau theory for layered superconductors. The theoretical results are compared with the experimental data for new superconductor LiFeAs. 相似文献
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采用二带Ginziburg-Landau(G-L)理论模型计算了各向异性超导体的上临界磁场,发现上临界磁场Hc2的解析式中包含序参量的各向异性和有效质量的各向异性;上临界磁场ab-面内分量Hc|2|ab、c-轴方向分量Hc|2|ab与实验数据符合;上临界磁场比率在实验许可范围之内。 相似文献
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Fermi surface topology and the upper critical field in two-band superconductors: application to MgB2
Recent measurements of the anisotropy of the upper critical field B(c2) on MgB2 single crystals have shown a puzzling strong temperature dependence. Here, we present a calculation of the upper critical field based on a detailed modeling of band structure calculations that takes into account both the unusual Fermi surface topology and the two gap nature of the superconducting order parameter. Our results show that the strong temperature dependence of the B(c2) anisotropy can be understood as an interplay of the dominating gap on the sigma band, which possesses a small c-axis component of the Fermi velocity, with the induced superconductivity on the pi-band possessing a large c-axis component of the Fermi velocity. We provide analytic formulas for the anisotropy ratio at T=0 and T=T(c) and quantitatively predict the distortion of the vortex lattice based on our calculations. 相似文献
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It is shown that the slope of the upper critical field
in superconductors with d pairing drops rapidly with increasing concentration of normal impurities, while in superconductors with anisotropic s pairing
increases and reaches the well-known asymptotic level characteristic for the isotropic case. This difference makes it possible,
in principle, to employ measurements of H
c
2 in disordered superconductors as an experimental method for determining the type of pairing in high-T
c
superconductors and systems with heavy fermions.
Pis’ma Zh. éksp. Teor. Fiz. 63, No. 5, 347–352 (10 March 1996) 相似文献
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C-axis oriented MgB_2 thin films were synthesized on single-crystal MgO (111) substrates using a chemical vapour deposition technique. The as-formed films revealed a sharp superconducting transition temperature of 38K with the transition width 0.2K. The temperature dependence of the upper critical magnetic field H_{c2}(T) in the films was determined via resistivity for magnetic field H parallel and perpendicular to the c axis of the films. Using the Werthamer-Helfand-Hohenberg formula, we obtained the anisotropy ratio of the upper critical field γ=1.2. 相似文献
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Xu Y Khafizov M Satrapinsky L Kús P Plecenik A Sobolewski R 《Physical review letters》2003,91(19):197004
Femtosecond pump-probe studies show that carrier dynamics in MgB2 films is governed by the sub-ps electron-phonon (e-ph) relaxation present at all temperatures, the few-ps e-ph process well pronounced below 70 K, and the sub-ns superconducting relaxation below T(c). The amplitude of the superconducting component versus temperature follows the superposition of the isotropic dirty gap and the three-dimensional pi gap dependences, closing at two different T(c) values. The time constant of the few-ps relaxation exhibits a double divergence at temperatures corresponding to the T(c)'s of the two gaps. 相似文献
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Lyard L Szabó P Klein T Marcus J Marcenat C Kim KH Kang BW Lee HS Lee SI 《Physical review letters》2004,92(5):057001
The temperature dependence of the upper (H(c2)) and lower (H(c1)) critical fields has been deduced from Hall probe magnetization measurements of high quality MgB2 single crystals along the two main crystallographic directions. We show that Gamma(H(c2))=H(c2 axially ab)/H(c2 axially c) and Gamma(H(c1))=H(c1 axially c)/H(c1 axially ab) differ significantly at low temperature (being approximately 5 and approximately 1, respectively) and have opposite temperature dependencies. We suggest that MgB2 can be described by a single field dependent anisotropy parameter gamma(H) (=lambda(c)/lambda(ab)=xi(ab)/xi(c)) that increases from Gamma(H(c1)) at low field to Gamma(H(c2)) at high field. 相似文献
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A. I. Posazhennikova M. V. Sadovskii 《Journal of Experimental and Theoretical Physics》1997,85(6):1162-1167
We carry out the Ginzburg-Landau expansion for superconductors with anisotropic s and d pairing in the presence of anisotropic normal-impurity scattering, which enhances the stability of d pairing with respect to disordering. We find that the slope of the curve of the upper critical field, |dH
c2/dT|T
c, in superconductors with d pairing behaves nonlinearly as disorder grows: at low scattering anisotropy the slope rapidly decreases with increasing impurity
concentration, then gradually but nonlinearly increases with concentration, reaches its maximum, and then rapidly decreases,
vanishing at the critical impurity concentration. In superconductors with anisotropic s pairing, |dH
c2/dT|T
c always increases with impurity concentration, finally reaching the familiar asymptotic value characteristic of the isotropic
case, irrespective of whether there is anisotropic impurity scattering.
Zh. éksp. Teor. Fiz. 112, 2124–2133 (December 1997) 相似文献
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R. Bausch E. Eisenriegler H. K. Janssen 《Zeitschrift für Physik B Condensed Matter》1979,36(2):179-186
We discuss nonlinear relaxation processes of the one-component Ginzburg-Landau field that occur near the critical point after a sudden change in temperature or in the symmetry breaking field. A universal form of the equation of motion for the order parameter at the one-loop level is derived and integrated for several cases of interest. From the results some characteristic universal amplitude ratios can be extracted. 相似文献
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用两带Ginzburg-Landau(GL)理论分析了Lu2Fe3Si5的表面临界磁场,当超导体的表面与任一主晶面重合,且外磁场平行于超导体的表面时,比值Hc3/Hc2(HC2是Lu2Fe3Si5的上临界磁场)强烈依赖于温度. 当超导体的表面是bc平面,且
关键词:
两带超导体
GL理论
2Fe3Si5')" href="#">Lu2Fe3Si5
表面临界磁场 相似文献
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Putti M Affronte M Ferdeghini C Manfrinetti P Tarantini C Lehmann E 《Physical review letters》2006,96(7):077003
We report specific heat measurements on neutron-irradiated MgB2 samples, for which the critical temperature is lowered to 8.7 K, but the superconducting transition remains extremely sharp, indicative of a defect structure extremely homogeneous. Our results evidence the presence of two superconducting gaps in the temperature range above 21 K, while single-gap superconductivity is well established as a bulk property, not associated with local disorder fluctuations, when Tc decreases to 11 K. 相似文献
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Lei Chen Jing Zuo Yanyan Lu Hai Huang 《Physica C: Superconductivity and its Applications》2011,471(23-24):1591-1594
Based on two-band Ginzburg–Landau theory, we study the temperature dependence of upper critical field for superconducting crystal NbSe2. The results reproduce the experimental data in a broad temperature range, especially the upward curvature near the transition temperature. Our calculations also indicate that in NbSe2 the band with the smaller gap is almost isotropic, and most probably located on the bonding Nb Fermi sheets. 相似文献