scholarly journals The Energy Dependence Of The Effective Interaction In Superconductivity

1966 ◽  
Vol 19 (4) ◽  
pp. 509
Keyword(s):  
Experimental Data ◽  
Integral Equation ◽  
Critical Temperature ◽  
Specific Heat ◽  
Critical Field ◽  
Energy Gap ◽  
Effective Interaction ◽  
Electronic Specific Heat ◽  
First Order ◽  
Energy Dependent

The effective interaction in the BCS model of superconductivity is usually approximated by a constant. We expand the interaction in a power series in <k/llw and treat the energy-dependent terms to first order. This introduces one more parameter in the theory. The gap, which now becomes energy dependent, is obtained by solving an integral equation by iteration. The critical field and specific heat are calculated. The value of 2~(0,0)/kBTe and the jump in the electronic specific heat at the critical temperature Te are now dependent on the parameters of the superconductor. Calculated values for the energy gap and the critical field He agree rather well with the experimental data.

CRITICAL BEHAVIOR OF THE SPECIFIC HEAT IN THE VICINITY OF THE TRANSITION TEMPERATURE FOR S-TRIAZINE

2009 ◽  
Vol 23 (09) ◽  
pp. 2253-2259 ◽  
Author(s):  
M. KURT ◽  
H. YURTSEVEN
Keyword(s):  
Experimental Data ◽  
Phase Transition ◽  
Transition Temperature ◽  
Critical Exponent ◽  
Specific Heat ◽  
Power Law ◽  
Order Phase Transition ◽  
Critical Behavior ◽  
First Order ◽  
Second Order Phase Transition

The critical behavior of the specific heat is studied in s-triazine ( C 3 N 3 H 3). Using the experimental data for the CP, the temperature dependence of the specific heat is analyzed according to a power-law formula and the values of the critical exponent for CP are extracted in the vicinity of the transition temperature (TC=198.07 K ). It is indicated that s-triazine undergoes a weakly first order (quasi-continuous) or second order phase transition.

Superconductivity of tin isotopes

1951 ◽  
Vol 47 (4) ◽  
pp. 811-819 ◽  
Author(s):  
J. M. Lock ◽  
A. B. Pippard ◽  
D. Shoenberg
Keyword(s):  
Transition Temperature ◽  
Magnetic Fields ◽  
Specific Heat ◽  
Critical Field ◽  
Electronic Specific Heat ◽  
Transition Temperatures ◽  
Superconducting Transition ◽  
Critical Magnetic Fields ◽  
The Law

AbstractDetailed measurements have been made of the superconducting transition temperatures and critical magnetic fields of the tin isotopes of mass 116, 120 and 124. The transition temperature varies with isotopic mass according to the law Tc ∞ M−n, with n = 0·462 ± 0·014, a result very similar to that already found in mercury. The critical field curves of isotopes 116 and 124 are geometrically similar, in the sense that both many be represented by the same equation, Hc/Ho = f(T/Tc), with the same ratio Ho/Tc for both. It is deduced that the electronic specific heat in normal tin varies only slowly, if at all, with isotopic mass. The variation of Tc and Ho with M is very close to that predicted by Fröhlich and Bardeen.

Nuclear Spin–Lattice Relaxation in Superconducting Al

1972 ◽  
Vol 50 (6) ◽  
pp. 563-566 ◽  
Author(s):  
J. P. Carbotte ◽  
P. T. Truant
Keyword(s):  
Experimental Data ◽  
Critical Temperature ◽  
Relaxation Rate ◽  
Nuclear Spin ◽  
Energy Gap ◽  
Microscopic Theory ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Spin Lattice ◽  
Nuclear Spin Lattice Relaxation

We have calculated the temperature variation of the nuclear spin–lattice relaxation rate in superconducting aluminum taking account of the anisotropy in the energy gap that Leavens and Carbotte have recently calculated from microscopic theory. We compare this variation with the available experimental data for the region near the critical temperature.

scholarly journals An experiment on the mechanism of superconductivity

1946 ◽  
Vol 185 (1001) ◽  
pp. 225-239 ◽  
Keyword(s):  
Specific Heat ◽  
Energy Gap ◽  
Absolute Zero ◽  
Magnetic Data ◽  
Electronic Specific Heat ◽  
Small Energy ◽  
Electronic Term ◽  
Apparent Specific Heat ◽  
Direct Experiment ◽  
Thomson Coefficient

The Thomson coefficient of superconductive lead has been determined by a direct experiment and found to be zero (<4x 10 -9 V/deg.). It has been concluded from this result that the electrons engaged in a superconductive current remain energetically at absolute zero. The apparent electronic specific heat of a superconductor is assumed to be due to an excitation of electrons from the lowest state. The magnetic data suggest that this apparent specific heat is proportional to T 3 . A purely empirical model of the electronic term system for a superconductor has been suggested in which a small energy gap ( ~10 -4 eV) separates the upper limit of the Fermi distribution at absolute zero from a continuum of higher states. The frictionless transport of electrons is supposed to be due to metastable states within the gap in which energy cannot be dissipated. In such a model the number of superconductive electrons at absolute zero has been calculated to be of the order of 10 -3 of the number of atoms. Attention has been drawn to a peculiar similarity between the frictionless transport in superconductors and that in liquid helium II. It has been concluded that the cause for both phenomena may be essentially the same—an aggregation of freely mobile particles of zero thermal energy which follows similar rules irrespective of the nature of the particles involved.

Anomalies in Physical Properties Related to the Stability of the B2-Phase in Ti-Ni-Co Shape Memory Alloys

2005 ◽  
Vol 475-479 ◽  
pp. 1977-1982 ◽  
Author(s):  
Mi Seon Choi ◽  
Takashi Fukuda ◽  
Tomoyuki Kakeshita
Keyword(s):  
Electrical Resistivity ◽  
Magnetic Susceptibility ◽  
Martensitic Transformation ◽  
Specific Heat ◽  
Nucleation And Growth ◽  
Electronic Specific Heat ◽  
Transformation Behavior ◽  
First Order ◽  
The Stability ◽  
Specific Heat Coefficient

Martensitic transformation behavior of a series of Ti-(50-x)Ni-xCo at% alloys (x = 4, 8, 12, 16, 20) has been examined by electrical resistivity, magnetic susceptibility and specific heat measurements, in order to know the phase stability of the B2-type structure. The 4Co and 8Co alloys exhibit a typical first order B2-R-B19' transformation. The 12Co alloy probably transforms to the R-phase, but its microstructure is composed of small domains with about 10 nm in diameter, being quite different from the microstructure of a typical R-phase formed by nucleation and growth. The 16Co and the 20Co alloys do not show any martensitic transformation but anomalies of the electrical resistivity and magnetic susceptibility being similar to those of the 12Co alloy appear in these alloys. The diffuse scattering of 1/3<110> is also observed in the 16Co alloy. The Debye temperature decreases and electronic specific heat coefficient increases with increasing Co content.

ON THE FERMI SURFACE OF BETA BRASS

1966 ◽  
Vol 44 (8) ◽  
pp. 1787-1793 ◽  
Author(s):  
J. -P. Jan
Keyword(s):  
Fermi Surface ◽  
Specific Heat ◽  
Brillouin Zone ◽  
Present Model ◽  
Energy Gap ◽  
Electronic Specific Heat ◽  
Cone Model ◽  
Best Fit ◽  
Structure Calculations ◽  
Good Agreement

Results of de Haas – van Alphen effect measurements on ordered β′-CuZn (50 at.% Zn) provide the area of contact of the Fermi surface with the faces of the second (dodecahedral) Brillouin zone. If the energy gaps at the faces of the first (cubic) Brillouin zone are ignored, a 12-cone model can be worked out. An energy gap of 3.49 eV at the second-zone faces and an effective mass m* = 1.045me, provide the best fit between the 12-cone model, the area of contact, and the measured electronic specific heat. The gap is in good agreement with present band-structure calculations. The first-zone gaps do give rise to de Haas – van Alphen oscillations, but their neglect in the present model should not affect the calculated electronic specific heat appreciably.

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