Unconventional superconductivity mediated solely by isotropic electron-phonon interaction

Schrodi, Fabian; Oppeneer, Peter M.; Aperis, Alex

doi:10.1103/physrevb.104.l140506

Cited by 14 publications

(12 citation statements)

References 39 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We assume that the phonons are dispersionless Einstein phonons ω q = ω E and that the coupling g q is isotropic, g q = g/ √ N. The same model was used for flat-band systems in Refs. [28,29], and similar models have been applied in numerous systems [34,35,61,67,70,86]. Simplifying to Einstein phonons with isotropic coupling removes the k dependence on the right-hand side of the Eliashberg equations in Appendix A, and then the Eliashberg functions depend only on frequency.…”

Section: Green's Function Derivation Of Eliashberg Equationsmentioning

confidence: 99%

Exceeding the Chandrasekhar-Clogston limit in flat-band superconductors: A multiband strong-coupling approach

Mæland,

Sudbø

2023

Phys. Rev. B

View full text Add to dashboard Cite

Hybrid systems of superconductors and magnets display several intriguing properties, both from a fundamental physics point of view and with practical applications. Promising applications in superconducting spintronics motivate a search for systems where superconductivity can survive larger in-plane critical magnetic fields than the conventional limit. The Chandrasekhar-Clogston (CC) limit applies to thin-film conventional superconductors with in-plane magnetic fields such that orbital effects may be ignored. For a magnetic field strength comparable to the superconducting gap at zero temperature and zero field, a spin-split normal state attains lower free energy than the superconducting state. A multiband superconductor with a flat band placed just below the Fermi surface has been shown to surpass the CC limit using weak-coupling theory. Since the dimensionless coupling determining the critical temperature scales with the density of states, it is natural to anticipate corrections from strong-coupling theory in flat-band systems, owing to the large density of states of the flat bands. We derive Eliashberg equations and the free energy for a multiband superconductor in a magnetic field. First, we show that the CC limit can be exceeded by a small amount in one-band strong-coupling superconductors due to self-energy renormalization of the magnetic field. Next, we consider a two-band system with one flat band and find that the CC limit can be exceeded by a large amount also in strong-coupling theory, even when including hybridization between bands that intersect.

show abstract

Section: Green's Function Derivation Of Eliashberg Equationsmentioning

confidence: 99%

Exceeding the Chandrasekhar-Clogston limit in flat-band superconductors: A multiband strong-coupling approach

Mæland,

Sudbø

2023

Phys. Rev. B

View full text Add to dashboard Cite

show abstract

“…The observation of a smaller ER compared to 2Δ provides evidence for the existence of a spin exciton. On the other hand, numerous experiments reported the evidence of electronphonon coupling in these materials [15][16][17][18][19][20][21][22][23][24][25] , and other proposals of pairing glue such as orbital fluctuations [26][27][28] , add more complexity to the investigation of unconventional superconductivity.…”

Section: Introductionmentioning

confidence: 99%

Evidence of electron interaction with an unidentified bosonic mode in superconductor CsCa2Fe4As4F2

Jiang,

Li,

Liao

et al. 2024

Preprint

View full text Add to dashboard Cite

Using angle-resolved photoemission spectroscopy, we report the evidence of the observation of a kink structure in the band dispersion of Fe-based superconductor CsCa2Fe4As4F2. The kink shows an orbital selective and momentum dependent behavior, which is located at 15 meV below Fermi level along the Γ - M direction at the band with dxz orbital character and vanishes when approaching the Γ - X direction, correlated with a slight decrease of the superconducting gap. Most importantly, this kink structure disappears when the superconducting gap closes, indicating that the corresponding bosonic mode (~ 9 ± 1 meV) is closely related to superconductivity. However, the origin of this mode remains unidentified, since it cannot be related to phonons or the spin resonance mode (~ 15 meV) observed by inelastic neutron scattering. The behavior of this mode is rather unique and challenges our present understanding of the superconducting paring mechanism of the bilayer FeAs-based superconductors.

show abstract

“…In the current work we follow this route, but we employ non-adiabatic Eliashberg theory, since it has been shown recently that including vertex corrections beyond Migdal's approximation can lead to negative contributions to the electron-phonon coupling [38], leading to an effectively attractive (repulsive) coupling at small (large) wave vectors, thereby overall supporting a d-wave symmetric superconducting gap [39]. Not only does the inclusion of second-order scattering events increase the coupling strength in the d-wave channel [40,41], it has also been shown that self-consistent non-adiabatic model calculations assuming an isotropic EPI can lead to the experimentally observed unconventional symmetry of the order parameter in slightly hole-doped cuprates [39,42]. Apart from the gap symmetry, the gap magnitude and critical temperature T c are similarly found to be in a realistic regime when employing vertex-corrected Eliashberg theory [39].…”

Section: Introductionmentioning

confidence: 99%

“…Not only does the inclusion of second-order scattering events increase the coupling strength in the d-wave channel [40,41], it has also been shown that self-consistent non-adiabatic model calculations assuming an isotropic EPI can lead to the experimentally observed unconventional symmetry of the order parameter in slightly hole-doped cuprates [39,42]. Apart from the gap symmetry, the gap magnitude and critical temperature T c are similarly found to be in a realistic regime when employing vertex-corrected Eliashberg theory [39].…”

Section: Introductionmentioning

confidence: 99%

Doping dependence and multichannel mediators of superconductivity: calculations for a cuprate model

Schrodi,

Aperis,

Oppeneer

2024

Electron. Struct.

View full text Add to dashboard Cite

We study two aspects of the superconductivity in a cuprate model system, its doping dependence and the influence of competing pairing mediators. We first include electron-phonon interactions beyond Migdal’s approximation and solve self- consistently, as a function of doping and for an isotropic electron-phonon coupling, the full-bandwidth, anisotropic vertex-corrected Eliashberg equations under a non-interacting state approximation for the vertex correction. Our results show that such pairing interaction supports the experimentally observed dx2−y2-wave symmetry of the superconducting gap, but only in a narrow doping interval of the hole-doped system. Depending on the coupling strength, we obtain realistic values for the gap magnitude and superconducting critical temperature Tc close to optimal doping, rendering the electron-phonon mechanism an important candidate for mediating superconductivity in this model system. Second, for a doping near optimal hole doping, we study multichannel superconductivity, by including both vertex-corrected electron- phonon interaction and spin and charge fluctuations as pairing mechanisms. We find that both mechanisms cooperate to support an unconventional d-wave symmetry of the order parameter, yet the electron-phonon interaction is mainly responsible for the Cooper pairing and high critical temperature Tc. Spin fluctuations are found to have a suppressing effect on the gap magnitude and critical temperature due to their repulsive interaction at small coupling wave vectors.

show abstract

Unconventional superconductivity mediated solely by isotropic electron-phonon interaction

Cited by 14 publications

References 39 publications

Exceeding the Chandrasekhar-Clogston limit in flat-band superconductors: A multiband strong-coupling approach

Exceeding the Chandrasekhar-Clogston limit in flat-band superconductors: A multiband strong-coupling approach

Evidence of electron interaction with an unidentified bosonic mode in superconductor CsCa2Fe4As4F2

Doping dependence and multichannel mediators of superconductivity: calculations for a cuprate model

Contact Info

Product

Resources

About