Functional derivatives for the critical magnetic field of Pb

1978 ◽  
Vol 56 (9) ◽  
pp. 1248-1254 ◽  
Author(s):  
J. M. Daams ◽  
J. P. Carbotte
Keyword(s):  
Magnetic Field ◽  
Critical Temperature ◽  
Critical Field ◽  
Coulomb Repulsion ◽  
Critical Magnetic Field ◽  
Deviation Function ◽  
Functional Derivatives ◽  
First Time ◽  
Reduced Temperature ◽  
Good Agreement

We have calculated for superconducting Pb in the dirty (isotropic) limit the following functional derivatives: δTc/δα2F(ω), δHc(0)/δα2F(ω), δD(t)/δα2F(ω), ∂Tc/∂μ*, ∂Hc(0)/∂μ*, and ∂D(t)/∂μ*, where Tc, Hc(0), D(t), t, α2(ω)F(ω), and μ* are, respectively, the critical temperature, critical field at T = 0, deviation function for the critical field, reduced temperature T/Tc, electron–phonon spectral density, and Coulomb repulsion parameter. Our values for the first two functional derivatives are in good agreement with previous work by Rainer and Bergmann. We present the others here for the first time to relate the observed changes in Tc, Hc(0), and D(t) under hydrostatic pressure to the change in α2(ω)F(ω) and μ*.

scholarly journals LOWER CRITICAL MAGNETIC FIELD OF SUPERCONDUCTING Rb3C60

1992 ◽  
Vol 06 (16n17) ◽  
pp. 1037-1042 ◽  
Author(s):  
V. BUNTAR ◽  
U. ECKERN ◽  
C. POLITIS
Keyword(s):  
Magnetic Field ◽  
Penetration Depth ◽  
High Field ◽  
Model Analysis ◽  
Critical Magnetic Field ◽  
Field Analysis ◽  
Zero Temperature ◽  
Bean Model ◽  
Good Agreement

The lower critical magnetic field Hc1 of superconducting Rb 3 C 60 (Tc=28.5 K ) is estimated by different methods. The zero temperature value is found to be given by Hc1=16.2±1.0 mT, and the penetration depth is λL=215±10 nm . The Bean model analysis leads to threshold fields of 5.3 mT for T=5 K , and 4.0 mT for T=17 K . The big influence of intergranular connections on Hc1 is demonstrated. Good agreement between the low- and the high-field analysis is found.

scholarly journals Meissner effect in holographic superconductors with Dirac–Born–Infeld electrodynamics

2019 ◽  
Vol 35 (06) ◽  
pp. 2050020
Author(s):  
Debabrata Ghorai ◽  
Sunandan Gangopadhyay ◽  
Rabin Banerjee
Keyword(s):  
Magnetic Field ◽  
Critical Temperature ◽  
Meissner Effect ◽  
Critical Magnetic Field ◽  
Matching Method ◽  
Holographic Superconductors

In this paper, we have investigated the Meissner effect of holographic superconductors in the presence of Dirac–Born–Infeld electrodynamics. The matching method is applied to obtain the critical magnetic field and the critical temperature. The critical magnetic field obtained from this investigation shows the effects of the DBI parameter [Formula: see text] and differs from that obtained from Born electrodynamics because of the extra [Formula: see text] term in the Dirac–Born–Infeld theory. It is observed that the critical magnetic field increases in Dirac–Born–Infeld theory compared to that in the Born theory.

scholarly journals Температурные зависимости критических параметров неоднородных сверхпроводящих пленок

2021 ◽  
Vol 63 (8) ◽  
pp. 1035
Author(s):  
П.И. Безотосный ◽  
К.А. Дмитриева
Keyword(s):  
Magnetic Field ◽  
Critical Temperature ◽  
External Magnetic Field ◽  
Critical Current Density ◽  
Critical Current ◽  
Current Density ◽  
Superconducting Films ◽  
Critical Magnetic Field ◽  
Temperature Dependences ◽  
Comparison Of The Results

The results of calculating the temperature dependences of the critical current density and critical magnetic field of thin inhomogeneous superconducting films are presented. Comparison of the results obtained for inhomogeneous films with the results of calculations for homogeneous ones showed that in both cases, the decrease in the critical magnetic field occurs according to the root law, and the critical current density changes according to a power law with a degree of 3/2 when approaching the critical temperature. Quantitatively, the critical current density for inhomogeneous films in the absence of an external magnetic field is lower than for homogeneous ones. In turn, the critical magnetic field of inhomogeneous films is much larger than the critical field of homogeneous films.

The Study on Surface Critical Magnetic Field of a Layered Magnetic Superconductors

2014 ◽  
Vol 979 ◽  
pp. 224-227 ◽  
Author(s):  
Sumitta Meakniti ◽  
Arpapong Changjan ◽  
Pongkaew Udomsamuthirun
Keyword(s):  
Magnetic Field ◽  
Magnetic Property ◽  
Variational Method ◽  
Critical Field ◽  
Landau Equation ◽  
Critical Magnetic Field ◽  
Ginzburg Landau ◽  
Ginzburg Landau Equation ◽  
Non Linear

In this research, we studied the surface critical magnetic field () of a layered magnetic superconductors by Ginzburg-Landau approach. After the 1st Ginzburg-Landau equation was calculated, a surface critical field was solved by variational method analytically. Our formula obtained was depended on the magnetic property of superconductor. We found that Hc3 of antiferromagnetism and paramagnetism superconductors were shown the same behaviour as non-magnetic superconductors. For diamagnetism and ferromagnetism superconductors, the higher and the lower values of critical magnetic field were found, respectively. However, the Hc3 was strongly depended on the non-linear of magnetic field intend of all kind magnetism.

The Behavior of the Critical Magnetic Field and Correlation Functions in Finite-Size Hubbard-Like Models

1997 ◽  
Vol 11 (01n02) ◽  
pp. 147-152
Author(s):  
A.N. Kocharian
Keyword(s):  
Magnetic Field ◽  
Critical Field ◽  
Finite Size ◽  
Spin Correlation ◽  
Critical Magnetic Field ◽  
Spin Liquid ◽  
Lattice Geometry ◽  
Half Filling ◽  
Spin Flips ◽  
Spin Liquid State

We present exact analytical results for a critical field and correlations functions for N site ring and arbitrary size two dimensional coupled chains in a two component Hubbard model with a strong magnetic field and exactly at half-filling. The critical field near the Nagaoka instability with one spin and two spin flips is driven by Coulomb interaction, lattice geometry, dimensionality and crucially depends on the number of atomic sites N. Unsaturated ferromagnetism, reminiscent of Nagaoka-like behavior, and spin liquid state are examined in the structure of off-diagonal spin correlation at large U.

scholarly journals MAGNETIC FIELD INDUCED GAP AND KINK BEHAVIOR OF THERMAL CONDUCTIVITY

2002 ◽  
Vol 16 (04) ◽  
pp. 107-116 ◽  
Author(s):  
E. J. FERRER ◽  
V. P. GUSYNIN ◽  
V. DE LA INCERA
Keyword(s):  
Magnetic Field ◽  
Thermal Conductivity ◽  
External Magnetic Field ◽  
Critical Field ◽  
Applied Magnetic Field ◽  
Interaction Model ◽  
Critical Magnetic Field ◽  
Landau Levels

The thermal conductivity of a quasiparticle (QP) system described by a relativistic four-fermion interaction model in the presence of an external magnetic field is calculated. It is shown that, for narrow widths of quasiparticles, the thermal conductivity, as a function of the applied magnetic field, exhibits a kink behavior at a critical field B c ~ T2. The kink is due to the opening of a gap in the QP spectrum at a critical magnetic field B c and to the enhancement of the transitions between the zeroth and first Landau levels. Possible applications of the results are discussed.

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.

scholarly journals Holographic superconductors in Born–Infeld electrodynamics and external magnetic field

2014 ◽  
Vol 29 (17) ◽  
pp. 1450088 ◽  
Author(s):  
Sunandan Gangopadhyay
Keyword(s):  
Magnetic Field ◽  
Critical Temperature ◽  
External Magnetic Field ◽  
Critical Magnetic Field ◽  
Field Equations ◽  
Holographic Superconductor ◽  
Holographic Superconductors

In this paper, we analytically investigate the effect of adding an external magnetic field in the presence of Born–Infeld (BI) corrections to a holographic superconductor in the probe limit. The technique employed is based on the matching of the solutions to the field equations near the horizon and the asymptotic AdS region. We obtain expressions for the critical temperature and the condensation values explicitly to all orders in the BI parameter. The value of the critical magnetic field is finally obtained and is found to get affected by the BI parameter.

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