Josephson-coupled layered superconductors with two order parameters. I. Upper critical magnetic field

1994 ◽  
Vol 6 (11) ◽  
pp. 2245-2258 ◽  
Author(s):  
E P Nakhmedov ◽  
E V Tahirov
Keyword(s):  
Magnetic Field ◽  
Critical Magnetic Field ◽  
Order Parameters ◽  
Layered Superconductors ◽  
Upper Critical Magnetic Field

Superconducting Fractal Multilayers

Fractals ◽  
1997 ◽  
Vol 05 (supp02) ◽  
pp. 101-117
Author(s):  
A. S. Sidorenko
Keyword(s):  
Magnetic Field ◽  
Angular Dependence ◽  
Fractal Dimensionality ◽  
High Energy ◽  
Critical Magnetic Field ◽  
Superconducting Film ◽  
Two Dimensional ◽  
Layered Superconductors ◽  
Upper Critical Magnetic Field ◽  
Critical Magnetic Fields

The influence of fractal geometry on superconductivity has been studied for layered superconductors. Superconducting multilayers consisting of alternating Nb and Cu layers with fractal stacking sequence and fractal dimension Df=0.63 including the two limiting cases Df= 0 (single superconducting film) and Df=1 (periodic multilayers) were prepared by electron-beam evaporation in ultrahigh vacuum. The layers of Nb and Cu were put down alternately via computer control of the target shutter. The structure of the samples has been checked with in situ reflection high-energy electron diffraction (RHEED) and Auger depth profiling, confirmed the prescribed layering geometry. Superconductivity was investigated by measurements of the critical temperature of superconducting transition Tc, and of the temperature and of the angular dependence of the upper critical magnetic fields Bc2. The observed dependences of Tc on the parameters of fractal samples are in a good qualitative agreement with the proximity effect theory developed for layered superconductors with a self-similar fractal structure. The behavior of the upper critical magnetic field is directly related to the type of the layering. At low temperatures, all samples show the same two-dimensional behavior essentially governed by the topological dimension of the individual superconducting layers, independent of the fractal dimensionality Df of the samples, whereas for temperatures near Tc the type of layering determines the dimensionality, resulting in a multicrossover behavior of fractal samples. The angular dependence of the upper critical magnetic field Bc2(θ) of fractals corresponds to the theory for a two-dimensional superconductor at all temperatures, reflecting the multicrossover behavior of the fractal multilayers, as long as the temperature-dependent coherence length is comparable with a certain scale of fractal.

Upper Critical Magnetic Field of the Heavy-Fermion Superconductor UBe13

1985 ◽  
Vol 54 (5) ◽  
pp. 477-480 ◽  
Author(s):  
M. B. Maple ◽  
J. W. Chen ◽  
S. E. Lambert ◽  
Z. Fisk ◽  
J. L. Smith ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Heavy Fermion ◽  
Critical Magnetic Field ◽  
Upper Critical Magnetic Field ◽  
Heavy Fermion Superconductor

scholarly journals Theoretical Study of Upper Critical Magnetic Field (HC2) in Multiband Iron Based Superconductors

2016 ◽  
Vol 2016 ◽  
pp. 1-10 ◽  
Author(s):  
Tsadik Kidanemariam ◽  
Gebregziabher Kahsay
Keyword(s):  
Magnetic Field ◽  
Phase Diagrams ◽  
Penetration Depth ◽  
Coherence Length ◽  
Symmetry Axis ◽  
Critical Magnetic Field ◽  
Ginzburg Landau ◽  
Iron Based Superconductors ◽  
Upper Critical Magnetic Field ◽  
Iron Based

This research work focuses on the theoretical investigation of the upper critical magnetic field,HC2; Ginzburg-Landau coherence length,ξGL(T); and Ginzburg-Landau penetration depth,λGL(T), for the two-band iron based superconductorsBaFe2(As1-xPx)2,NdO1-xFxFeAs, and LiFeAs. By employing the phenomenological Ginzburg-Landau (GL) equation for the two-band superconductorsBaFe2(As1-xPx)2,NdO1-xFxFeAs, and LiFeAs, we obtained expressions for the upper critical magnetic field,HC2; GL coherence length,ξGL; and GL penetration depth,λGL, as a function of temperature and the angular dependency of upper critical magnetic field. By using the experimental values in the obtained expressions, phase diagrams of the upper critical magnetic field parallel,HC2∥c, and perpendicular,HC2⊥c, to the symmetry axis (c-direction) versus temperature are plotted. We also plotted the phase diagrams of the upper critical magnetic field,HC2versus the angleθ. Similarly, the phase diagrams of the GL coherence length,ξGL, and GL penetration depth,λGL, parallel and perpendicular to the symmetry axis versus temperature are drawn for the superconductors mentioned above. Our findings are in agreement with experimental observations.

scholarly journals Restoration of superconductivity in high magnetic fields in UTe2

2020 ◽  
Vol 34 (32) ◽  
pp. 2030007
Author(s):  
Andrei G. Lebed
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Superconducting State ◽  
Critical Magnetic Field ◽  
High Magnetic Fields ◽  
Two Dimensional ◽  
Upper Critical Magnetic Field ◽  
Reentrant Superconductivity ◽  
Theoretical Results ◽  
General Method

It was theoretically predicted more than 20 years ago [A. G. Lebed and K. Yamaji, Phys. Rev. Lett. 80, 2697 (1998)], that a triplet quasi-two-dimensional (Q2D) superconductor could restore its superconducting state in parallel magnetic fields, which are higher than its upper critical magnetic field, [Formula: see text]. It is very likely that, recently, such phenomenon has been experimentally discovered in the Q2D superconductor UTe2 by Nicholas Butch, Sheng Ran, and their colleagues and has been confirmed by Japanese–French team. We review our previous theoretical results using such a general method that it describes the reentrant superconductivity in the abovementioned compound and will hopefully describes the similar phenomena, which can be discovered in other Q2D superconductors.

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