scholarly journals Reduction of superconducting transition temperature and flux pinning in Al and C codoped MgB2 with insight from first-principles calculations

2008 ◽  
Vol 103 (7) ◽  
pp. 07C713 ◽  
Author(s):  
A. H. Li ◽  
X. L. Wang ◽  
S. X. Dou ◽  
Q. W. Yao ◽  
Z. X. Cheng ◽  
...  
Keyword(s):  
Transition Temperature ◽  
First Principles ◽  
Superconducting Transition Temperature ◽  
Flux Pinning ◽  
Superconducting Transition ◽  
First Principles Calculations

scholarly journals Unconventional Co-Existence of Insulating Nano-Regions and Conducting Filaments in Reduced SrTiO3: Mode Softening, Local Piezoelectricity, and Metallicity

Crystals ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 437
Author(s):  
Annette Bussmann-Holder ◽  
Hugo Keller ◽  
Arndt Simon ◽  
Gustav Bihlmayer ◽  
Krystian Roleder ◽  
...  
Keyword(s):  
Transition Temperature ◽  
Carrier Concentration ◽  
Superconducting Transition Temperature ◽  
Superconducting Transition ◽  
First Principles Calculations ◽  
Effective Electron ◽  
Mode Softening ◽  
Component Type ◽  
Electron Phonon Coupling ◽  
Transverse Optic

Doped SrTiO3 becomes a metal at extremely low doping concentrations n and is even superconducting at n < 1020 cm−3, with the superconducting transition temperature adopting a dome-like shape with increasing carrier concentration. In this paper it is shown within the polarizability model and from first principles calculations that up to a well-defined carrier concentration nc transverse optic mode softening takes place together with polar nano-domain formation, which provides evidence of inhomogeneity and a two-component type behavior with metallicity coexisting with polarity. Beyond this region, a conventional metal is formed where superconductivity as well as mode softening is absent. For n ≤ nc the effective electron-phonon coupling follows the superconducting transition temperature. Effusion measurements, as well as macroscopic and nanoscopic conductivity measurements, indicate that the distribution of oxygen vacancies is local and inhomogeneous, from which it is concluded that metallicity stems from filaments which are embedded in a polar matrix as long as n ≤ nc.

Use of rescreened pseudopotentials for the superconductivity of aluminum at finite pressures

1981 ◽  
Vol 59 (3) ◽  
pp. 309-314 ◽  
Author(s):  
M. D. Whitmore
Keyword(s):  
Transition Temperature ◽  
Pressure Dependence ◽  
First Principles ◽  
Superconducting Transition Temperature ◽  
Imaginary Axis ◽  
Superconducting Transition ◽  
Volume Changes ◽  
Source Of Error ◽  
Coulomb Pseudopotential ◽  
Phonon Properties

Use is made of the pseudopotential determined by Dagens, Rasolt, and Taylor to calculate from first principles all the microscopic phonon and electron–phonon properties necessary for the superconducting transition temperature of aluminum, Tc, for zero pressure and for volume changes up to −10%. After fitting the Coulomb pseudopotential parameter μ* at zero pressure, Tc is calculated both by solving the Eliashberg gap equations on the imaginary axis, and by employing the approximate formulae of McMillan and of Leavens. The resulting pressure dependence of Tc is unsatisfactory. One source of error appears to be an insufficient pressure-induced shift of the phonon frequencies, indicating a limitation on the use of these pseudopotentials that is not widely appreciated. However, this is not believed to be the only difficulty and other possibilities are briefly discussed.

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.

Sign in / Sign up

Export Citation Format

Share Document