Relevance of quadratic electron-phonon coupling for the superconducting transition temperature

ABSTRACTThe superconducting transition temperature, Tc, of a series of non-transition metals was improved by implantation of H and D into these metals kept below 10 K. In all cases the increase of Tc was considerably larger for H and D implantation with respect of He implantation causing only radiation effects. It could be shown that the enhancement of Tc depends on the electron-phonon coupling constant of the host metal, suggesting that mainly phonon effects dominate the improvement of Tc.

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

Crystals ◽

10.3390/cryst10060437 ◽

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.

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A First-Principles Study of Electron-Phonon Coupling of OsB2

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.597.113 ◽

2014 ◽

Vol 597 ◽

pp. 113-116

Author(s):

Yue Qin Wang ◽

Juan Gao ◽

Shao Ping Yan

Keyword(s):

Transition Temperature ◽

First Principles ◽

Linear Response ◽

Lattice Dynamics ◽

Superhard Material ◽

Superconducting Transition ◽

Phonon Coupling ◽

Phonon Modes ◽

Electron Phonon Coupling ◽

Coulomb Pseudopotential

We investigated the lattice dynamics and electron-phonon coupling (EPC) of superhard material OsB2by first-principles linear response calculations. The calculated EPC parameters for the optical phonon modes at Г indicate that the heavy Os atoms play the most important role in deciding the superconducting behavior, and there are sizeable contributions from lighter B atoms to EPC. Our calculated EPC constant is 0.42, and the estimated superconducting transition temperatureTcis 2.1 K using the Coulomb pseudopotentialμ*=0.125, in excellent agreement with the experimental ones.

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ELECTRON–PHONON PAIRING IN THE HUBBARD MODEL

Modern Physics Letters B ◽

10.1142/s0217984992000624 ◽

1992 ◽

Vol 06 (09) ◽

pp. 541-546 ◽

Cited By ~ 6

Author(s):

N. M. PLAKIDA ◽

V. S. UDOVENKO

Keyword(s):

Transition Temperature ◽

Hubbard Model ◽

Function Technique ◽

Superconducting Transition ◽

Strong Correlations ◽

Phonon Coupling ◽

Phonon Interaction ◽

Electron Phonon Interaction ◽

Electron Phonon Coupling ◽

The Green Function

A system of electrons with strong correlations is considered within the framework of a single-band Hubbard model with a strong anharmonic electron-phonon interaction. The dependence of superconducting transition temperature T c on carrier concentration n is obtained using the Green function technique. It is shown that, due to the nonlocal character of electron–phonon coupling in the model, T c (n) strongly depends on the symmetry of the gap.

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Enhancing Superconductivity of the Nonmagnetic Quasiskutterudites by Atomic Disorder

Materials ◽

10.3390/ma13245830 ◽

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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