An electron tunneling investigation of quench-condensed superconductors

1970 ◽  
Vol 48 (23) ◽  
pp. 2783-2803 ◽  
Author(s):  
J. D. Leslie ◽  
J. T. Chen ◽  
T. T. Chen
Keyword(s):  
Transition Temperature ◽  
Energy Function ◽  
Phonon Spectrum ◽  
Energy Gap ◽  
Electron Tunneling ◽  
Coupling Theory ◽  
Complex Energy ◽  
Self Energy ◽  
Coulomb Pseudopotential ◽  
Theory Of Superconductivity

An electron tunneling investigation has been carried out on quench-condensed Bi, Ga, Pb, Pb∙75Bi∙25, Pb∙50Bi∙50, and Pb∙25Bi∙75. The energy gap and transition temperature have been measured for each sample. The tunneling derivative data have been analyzed in terms of the strong-coupling theory of superconductivity by means of a computer program of W. L. McMillan. The effective phonon spectrum, the Coulomb pseudopotential, the complex energy gap function, the pairing self-energy function, and the electron renormalization function have been determined for each sample. Certain parameters based on integrals over the phonon spectrum have also been calculated for each sample.

On a General Formula for the Transition Temperature of Superconductors

1974 ◽  
Vol 29 (3) ◽  
pp. 445-451 ◽  
Author(s):  
W. Kessel
Keyword(s):  
Transition Temperature ◽  
Integral Equations ◽  
General Formula ◽  
Transition Point ◽  
Energy Gap ◽  
Eliashberg Equations ◽  
Operator Form ◽  
Method Of Solution ◽  
Theory Of Superconductivity ◽  
Phonon Properties

A method of solution of the Eliashberg equations in the theory of superconductivity is derived which uses the fact that near the transition point the energy gap is small compared to the energies over which the electron-phonon properties vary appreciably. On this basis the Eliashberg equations are converted into linear inhomogeneous integral equations. Their solution is given in operator form and provides a general formula for the transition temperature

ELECTRON TUNNELING MEASUREMENTS OF ENERGY GAP IN SUPERCONDUCTORS YBaCuO, LaSrCuO AND BPBO

1987 ◽  
Vol 01 (02) ◽  
pp. 555-559 ◽  
Author(s):  
Hongjie TAO ◽  
Yingfei CHEN ◽  
Li LU ◽  
Qiansheng YANG ◽  
Bairu ZHAO ◽  
...  
Keyword(s):  
Transition Temperature ◽  
Strong Coupling ◽  
Perovskite Structure ◽  
Energy Gap ◽  
Electron Tunneling ◽  
Point Contact ◽  
Tunneling Conductance ◽  
Temperature Ratio ◽  
Superconducting Energy Gap

We have carried out superconducting energy gap measurements for polycrystalline perovskite-structure superconductors YBaCuO, LaSrCuO and BPBO with point contact tunneling. The tunneling conductance curves for YBaCuO, LaSrCuO and BPBO show the energy gap to transition temperature ratio 2Δ/kTc =4.7, 7.8 and 5.05 respectively, which is consistant with the strong-coupling superconductivity.

scholarly journals Phonon self-energy effects in the superconducting energy gap ofMgB2point-contact spectra

2004 ◽  
Vol 69 (10) ◽  
Author(s):  
I. K. Yanson ◽  
S. I. Beloborod’ko ◽  
Yu. G. Naidyuk ◽  
O. V. Dolgov ◽  
A. A. Golubov
Keyword(s):  
Energy Gap ◽  
Self Energy ◽  
Superconducting Energy Gap

Unrelated BCS-like pairing pseudogap and critical superconducting transition temperature in various cuprate compounds

2018 ◽  
Vol 32 (18) ◽  
pp. 1850195
Author(s):  
S. Dzhumanov ◽  
E. X. Karimboev ◽  
Sh. S. Djumanov
Keyword(s):  
Transition Temperature ◽  
Superconducting Transition Temperature ◽  
Order Parameter ◽  
Cuprate Superconductors ◽  
Energy Gap ◽  
Characteristic Temperature ◽  
Superconducting Order Parameter ◽  
Superconducting Transition ◽  
Gap Formation ◽  
Arpes Data

The smooth evolution of the energy gap observed in the tunneling and angle-resolved photoemission spectra (ARPES) of high-[Formula: see text] cuprates with lowering the temperature from a pseudogap state above the critical temperature [Formula: see text] to a superconducting state below [Formula: see text], has been poorly interpreted as the evidence that the pseudogap must have the same origin as the superconducting order parameter, and therefore, must be related to [Formula: see text]. We argue that such an explanation of the tunneling gap and ARPES data is misleading. We show that the BCS-like energy gap (or pseudogap) opening in the electronic excitation spectrum of underdoped-to-overdoped cuprates at a characteristic temperature [Formula: see text] and the true superconducting order parameter appearing only at [Formula: see text] are unrelated. The superconducting phenomenon in unconventional cuprate superconductors is fundamentally different from the BCS-like pairing of fermionic quasiparticles, and the superconducting transition temperature [Formula: see text] is not determined by the BCS-like gap formation. The unusual superconducting order parameter in these high-[Formula: see text] materials appears at [Formula: see text] and coexists with the BCS-like gap (or pseudogap) below [Formula: see text].

NEUTRINO SELF-ENERGY AND DISPERSION EQUATION IN DENSE MATTER

1996 ◽  
Vol 11 (28) ◽  
pp. 5093-5108 ◽  
Author(s):  
A. PEREZ MARTINEZ ◽  
A. ZEPEDA ◽  
H. PEREZ ROJAS
Keyword(s):  
Energy Gap ◽  
Vector Boson ◽  
Dense Matter ◽  
Self Energy ◽  
Dispersion Equations ◽  
Negative Effective Mass ◽  
Loop Approximation ◽  
Asymmetric Case ◽  
Type Spectrum ◽  
The One

General expressions for the neutrino self-energy and dispersion equations are found in a medium at finite temperature and density. The neutrino self-energy is calculated in the one-loop approximation and using the unitary gauge. The singularities and the absorption mechanisms are discussed. The low momentum (as compared with the vector boson masses) limit of the self-energy is obtained and from it, the dispersion equations for the quasiparticles are found. These solutions exhibit a group velocity smaller than unity which decreases with increasing density and an energy gap leading to a superfluid-type spectrum. In the particle–antiparticle asymmetric case, a negative effective mass is found for neutrinos.

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