共查询到20条相似文献,搜索用时 15 毫秒
1.
I. N. Askerzade 《Technical Physics》2014,59(11):1728-1731
Time-dependent equations of the two-band Ginzburg-Landau model are simulated numerically. Calculations are performed for square thin films of the LiFeAs two-band superconductor in the vicinity of the superconducting transition temperature in the transverse magnetic field; the quasi-hexagonal nature of the vortex lattice in the intermediate state is demonstrated. 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
4.
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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The upper critical field of clean MgB2 is investigated
using the two-band layered Ginzburg--Landau (GL) theory. The
calculated results are fitted to the experimental data of clean
MgB2 crystal very well in a broad temperature range. Based
on the GL theory for clean superconductors, a phenomenological
theory for dirty superconductor is proposed. Selecting appropriate
parameters, two-band layered GL theory is successfully applied to
the crystal of Mg(B1-xCx)2 and the neutron
irradiation samples of MgB2. 相似文献
6.
The upper critical field in MgB2 is investigated in the framework
of the two-gap Ginzburg-Landau theory. A variational solution of linearized
Ginzburg-Landau equations agrees well with the Landau level expansion
and demonstrates that spatial distributions of the gap functions are different
in the two bands and change with temperature. The temperature variation of the ratio of two gaps
is responsible for the upward temperature dependence of in-plane Hc2
as well as for the deviation of its out-of-plane behavior from the standard angular dependence.
The hexagonal in-plane modulations of Hc2 can change sign with decreasing temperature. 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
8.
L. Tewordt 《Zeitschrift für Physik A Hadrons and Nuclei》1965,184(3):319-324
The upper critical field,H c2, is calculated in the temperature range close toT c for arbitrary values of the mean free path 1. The method is to treat the fourth-order term in the linearized differential equation for the gap parameter as a perturbation to the harmonic oscillator equation. The Nambu-Tuan term, which determines the structure of the “clean-limit” and “dirty-limit” parts of the fourth-order term, is calculated by means of the ladder diagram technique for impurity interaction lines. The result is that the magnitude of the slope of the curveH c2/√2H c κ versust=T/T c att=1 decreases monotonically from the value 0.41 to 0.12 as the ratio of the BCS coherence lengthξ 0 to the mean free path 1 increases from 0 to ∞. For 1?ξ 0 this slope is about 0.26. 相似文献
9.
The temperature dependence of the surface upper critical field,H c3, nearT c is calculated for arbitrary values of the mean free pathl by taking into account the fourthorder term of the generalized Ginzburg-Landau theory. For finitel the boundary condition is modified such that the normal derivative of the energy gap at the surface becomes positive. The slope of the curveH c3/H c2 versust=T/T c att=1 is found to decrease monotoneously from zero to ?1.040 as one goes from the “dirty” to the “clean” limit. 相似文献
10.
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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Angst M Puzniak R Wisniewski A Jun J Kazakov SM Karpinski J Roos J Keller H 《Physical review letters》2002,88(16):167004
The anisotropy gamma of the superconducting state of high quality single crystals of MgB2 was determined, using torque magnetometry with two different methods. The anisotropy of the upper critical field was found to be temperature dependent, decreasing from gamma approximately 6 at 15 K to 2.8 at 35 K. Reversible torque data near T(c) reveal a field dependent anisotropy, increasing nearly linearly from gamma approximately equal to 2 in zero field to 3.7 in 10 kOe. The unusual temperature dependence is a true bulk property and can be explained by nonlocal effects of anisotropic pairing and/or the k--> dependence of the effective mass tensor. 相似文献
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We investigated the behavior of the spin-triplet superconductor Sr2RuO4 ( T(c) approximately 1.5 K) under the magnetic fields parallel to the quasi-two-dimensional plane. The upper critical field H(c2) exhibits a clear fourfold anisotropy of about 3% at 0.35 K. Furthermore, we detected an additional transition feature below H(c2) in both the ac susceptibility and the specific heat. These second-transition features as well as the pronounced in-plane H(c2) anisotropy disappear above 0.8 K or under intentional field misalignment of less than 1 degrees. Most of these characteristics are consistent with the predicted emergence of the second superconducting phase with a line-node gap. 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
19.
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
20.
We analyze the behaviour of kinks and semiclassical bound states at finite temperatures by applying quantum statistics to the fluctuations which determine the quantum dynamics of these states. We consider two theories in one space dimension — the ?4 theory with a dynamical symmetry breaking and the Gross-Neveu model. For the ?4 theory, the one-loop temperature corrections are obtained by using temperature-dependent Green function techniques. We show that the same result can be obtained by applying quantum statistics to the fluctuations around the kink. For the Gross-Neveu model, the temperature dependence of the bound states, which correspond to time-independent field configurations, is obtained. We show that for every bound state there exists a critical temperature at which this state breaks up into its constituents. This critical temperature increases with the number of constituents of the bound state. 相似文献