Anwendung der Methode der Korrelationsfunktion auf die Berechnung der Richtungsabhängigkeit von Hc2 im kubischen Einkristall

1970 ◽  
Vol 25 (8-9) ◽  
pp. 1161-1168 ◽  
Author(s):  
Klaus-Dieter Harms
Keyword(s):  
Magnetic Field ◽  
Correlation Function ◽  
Critical Field ◽  
Upper Critical Field ◽  
Critical Magnetic Field ◽  
Higher Order ◽  
Eigenvalue Equation ◽  
Cubic Symmetry ◽  
Upper Critical Magnetic Field

Abstract The upper critical magnetic field for a monocrystalline superconductor with cubic symmetry is calculated using the Method of the Correlation Function. The symmetry of the system leads to an eigenvalue equation which is solved with perturbation-theoretic methods. The upper critical field is calculated for dirty superconductors in the lowest order for which anisotropy is present. For clean superconductors, a higher order is calculated. Some results are critically compared with those in a paper by HOHENBERG and WERTHAMER.

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.

CRITICAL FIELD AND MAGNETORESISTANCE OF SINGLE CRYSTAL TmNi2B2C

1999 ◽  
Vol 13 (29n31) ◽  
pp. 3715-3717 ◽  
Author(s):  
D. G. NAUGLE ◽  
K. D. D. RATHNAYAKA ◽  
K. CLARK ◽  
P. C. CANFIELD
Keyword(s):  
Magnetic Field ◽  
Transition Temperature ◽  
Single Crystal ◽  
Critical Field ◽  
Superconducting Transition Temperature ◽  
Magnetic Transition ◽  
Upper Critical Field ◽  
Superconducting Transition ◽  
Large Anisotropy ◽  
The Magnetic Field

In-plane resistance as a function of magnitude and direction of the magnetic field and the temperature has been measured for TmNi2B2C from above the superconducting transition temperature at 10.7 K to below the magnetic transition TN=1.5 K. The superconducting upper critical field HC2(T) exhibits a large anisotropy and structure in the vicinity of TN. The magnetoresistance above TC is large and changes sign as the direction of the magnetic field is rotated from in-plane to parallel with the c-axis.

UPPER CRITICAL FIELD OF UNCONVENTIONAL SUPERCONDUCTORS FROM CHEMICAL EQUILIBRIUM

1999 ◽  
Vol 13 (29n31) ◽  
pp. 3443-3448 ◽  
Author(s):  
A. KALLIO ◽  
J. HISSA ◽  
T. HÄYRYNEN ◽  
V. BRÄYSY
Keyword(s):  
Magnetic Field ◽  
Critical Field ◽  
Normal State ◽  
Chemical Equilibrium ◽  
Critical Density ◽  
Upper Critical Field ◽  
Universal Function ◽  
Zero Magnetic Field ◽  
Mathematical Treatment ◽  
Critical Fields

We have shown previously that many normal state properties of high Tc superconductors in zero magnetic field can be understood in terms of a single universal function f(t) in the scaled variable t=T/T*, where T* is connected with temperature independent gap 2Δ=2kBT*, which gives the binding energy of a pair in analogy with dissociation of molecules. The function f(t) determines the fraction of bosons (B++) and fermions (h+) at temperature T and it is obtained from the mathematical treatment of chemical equilibrium with respect to the reaction B++⇌ 2h+. Since for magnetic fields of reasonable strength the Zeeman energy is much smaller than the pseudo gap Δ~100K-800K, the function f(t) in the normal state is largely independent of magnetic field. The main effect of the magnetic field is to increase the tendency for bosons to localize. This means that the critical density nL for delocalization in the ab-plane direction and the critical density for superfluidity nc (≳ nL) both increase with magnetic field. This causes the corresponding temperatures TBL(H) and Tc(H) to go down with the field. Assuming a power law dependence nc(H)/nc(0)=1+AHμ, the upper critical fields for several heavy fermion compounds are shown to fall into a single curve. The purpose here is to show that the upper critical field Hc2(y) (y=Tc(H)/Tc(0)) can be expressed in a simple way in terms of f(t). We show that this theory predicts all the shapes of Hc2(y) observed in several unconventinal superconductors such as Tl 2 Ba 2 CuO 6+δ, with Tc=15 K.

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