scholarly journals Избыточная проводимость анизотропных неоднородных сверхпроводников при температуре выше критической

2019 ◽  
Vol 61 (9) ◽  
pp. 1599
Author(s):  
Т.И. Могилюк ◽  
П.Д. Григорьев ◽  
К.К. Кешарпу ◽  
И.А. Колесников ◽  
А.А. Синченко ◽  
...  
Keyword(s):  
Transition Temperature ◽  
Temperature Dependence ◽  
Superconducting Transition Temperature ◽  
Superconducting Transition ◽  
Electric Resistance ◽  
Conductivity Anisotropy ◽  
Number Of Layers ◽  
Anisotropic Superconductors ◽  
Bridge Structures ◽  
Current Flows

AbstractThe theoretical model of conductivity of a layered anisotropic normal metal containing small superconducting ellipsoidal granules with an arbitrary ratio of semiaxes is developed. Calculation data obtained under two simple approximations (self-consistent and Maxwell) are compared. The results may be applied in the analysis of the observed temperature dependence of the conductivity anisotropy in various anisotropic superconductors with the superconducting phase emerging in the form of isolated superconducting granules. The temperature dependence of the electric resistance along and across the conducting layers above and near the superconducting transition temperature is studied experimentally for bridge structures of a varying thickness. It is demonstrated that this resistance and even the effective superconducting transition temperature depend strongly on the bridge thickness (i.e., the number of layers through which the electric current flows). Note that significant differences were observed only for the resistance across the layers.

Correlation Between the Anomalous Pressure Dependence of the Superconducting Transition Temperature in Thallium and the Temperature Dependence of its Knight Shift

1974 ◽  
Vol 52 (8) ◽  
pp. 678-686 ◽  
Author(s):  
J. Schratter ◽  
D. Llewelyn Williams
Keyword(s):  
Transition Temperature ◽  
Temperature Dependence ◽  
Pressure Dependence ◽  
Superconducting Transition Temperature ◽  
Knight Shift ◽  
Superconducting Transition ◽  
Electronic Density ◽  
Nonlinear Variation ◽  
Volume Dependence ◽  
Increasing Temperature

A study of the Knight shift has been carried out on a single crystal of thallium. The isotropic Knight shift decreases with increasing temperature, showing a nonlinear variation which is most pronounced between 50 and 150 K. This behavior is correlated with the anomalous pressure dependence of the superconducting transition temperature at low pressure. From the superconducting data on pure Tl and Tl–Hg alloys, we extract the volume dependence of the electronic density of states, and use it to derive the temperature dependence of the Knight shift. The results agree with the observed data.

CRITICAL STATE IN THE Y-Ba-Cu-O CERAMICS

1990 ◽  
Vol 04 (04) ◽  
pp. 591-603 ◽  
Author(s):  
A. N. ARTEMOV ◽  
A. M. GRISHIN ◽  
V. N. KORENIVSKII ◽  
A. N. ULYANOV ◽  
V. A. KHOKHLOV
Keyword(s):  
Transition Temperature ◽  
Temperature Dependence ◽  
Critical State ◽  
Superconducting Transition Temperature ◽  
Superconducting Transition ◽  
Diamagnetic Response ◽  
Calculation Results ◽  
Granular Superconductors ◽  
Multiple Frequencies ◽  
Good Agreement

The temperature and field dependences of the Y-Ba-Cu-O ceramics susceptibility have been studied both experimentally and theoretically. These dependence have been used to reconstruct the temperature dependence of the critical current (j c (T) = j c (0)(1 − T/T c1 )3/2, j c (0) = 340 A/cm 2, T c1 = 94.6 K ) and the distribution of the granules with respect to the superconducting transition temperature (with the maximum at T c2 = 95.3 K and ∆T = 1.1 K ). Within the critical state concept diamagnetic response of the granular superconductors at fundamental and multiple frequencies has been calculated. The calculation results are in good agreement with the experimentally obtained susceptibility dependences and explain the different dependences of the diamagnetic response on the magnitude of the d.c. field and the amplitude of a.c. field.

THERMAL EXPANSION OF FERROMAGNETIC SUPERCONDUCTORS: POSSIBLE APPLICATION TO UGe2

2010 ◽  
Vol 24 (25n26) ◽  
pp. 5192-5201
Author(s):  
NOBUKUNI HATAYAMA ◽  
RIKIO KONNO
Keyword(s):  
Free Energy ◽  
Thermal Expansion ◽  
Transition Temperature ◽  
Temperature Dependence ◽  
Conduction Band ◽  
Superconducting Transition Temperature ◽  
Superconducting Transition ◽  
Thermal Expansion Coefficients ◽  
Expansion Coefficients ◽  
Majority Spin

We investigate the temperature dependence of thermal expansion of the ferromagnetic triplet superconductors and their thermal expansion coefficients below the superconducting transition temperature of a majority spin conduction band. The free energy of the ferromagnetic superconductors derived by Linder et al. is used. The superconducting gaps in the A2 phase of 3 He and with a node in UGe 2 are considered. By applying Takahashi's method to the free energy, i.e. by taking into account the volume dependence of the free energy explicitly, the temperature dependence of the thermal expansion and the thermal expansion coefficients is studied below the superconducting transition temperature of the majority spin conduction band. We find that we have anomalies of the thermal expansion in the vicinity of the superconducting transition temperatures and that we have divergence of the thermal expansion coefficients are divergent at the superconducting transition temperatures. The Grüneisen's relation between the temperature dependence of the thermal expansion coefficients and the temperature dependence of the specific heat at low temperatures is satisfied.

scholarly journals Enhancing Superconductivity of the Nonmagnetic Quasiskutterudites by Atomic Disorder

Materials ◽  
2020 ◽  
Vol 13 (24) ◽  
pp. 5830
Author(s):  
Andrzej Ślebarski ◽  
Maciej M. Maśka
Keyword(s):  
High Temperature ◽  
Transition Temperature ◽  
Superconducting Transition Temperature ◽  
High Temperature Superconductors ◽  
Superconducting Phase ◽  
Length Scale ◽  
Superconducting Transition ◽  
Atomic Disorder ◽  
Strong Inhomogeneity ◽  
Related Compounds

We investigated the effect of enhancement of superconducting transition temperature Tc by nonmagnetic atom disorder in the series of filled skutterudite-related compounds (La3M4Sn13, Ca3Rh4Sn13, Y5Rh6Sn18, Lu5Rh6Sn18; M= Co, Ru, Rh), where the atomic disorder is generated by various defects or doping. We have shown that the disorder on the coherence length scale ξ in these nonmagnetic quasiskutterudite superconductors additionally generates a non-homogeneous, high-temperature superconducting phase with Tc⋆>Tc (dilute disorder scenario), while the strong fluctuations of stoichiometry due to increasing doping can rapidly increase the superconducting transition temperature of the sample even to the value of Tc⋆∼2Tc (dense disorder leading to strong inhomogeneity). This phenomenon seems to be characteristic of high-temperature superconductors and superconducting heavy fermions, and recently have received renewed attention. We experimentally documented the stronger lattice stiffening of the inhomogeneous superconducting phase Tc⋆ in respect to the bulk Tc one and proposed a model that explains the Tc⋆>Tc behavior in the series of nonmagnetic skutterudite-related compounds.

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