Robustness of s-wave pairing symmetry in iron-based superconductors and its implications for fundamentals of magnetically driven high-temperature superconductivity

Abstract

Based on the assumption that the superconducting state belongs to a single irreducible representation of lattice symmetry, we propose that the pairing symmetry in all measured iron-based superconductors is generally consistent with the A 1g s-wave. Robust s-wave pairing throughout the different families of iron-based superconductors at different doping regions signals two fundamental principles behind high-T c superconducting mechanisms: (i) the correspondence principle: the short-range magnetic-exchange interactions and the Fermi surfaces act collaboratively to achieve high-T c superconductivity and determine pairing symmetries; (ii) the magnetic-selection pairing rule: superconductivity is only induced by the magnetic-exchange couplings from the super-exchange mechanism through cation-anion-cation chemical bonding. These principles explain why unconventional high-T c superconductivity appears to be such a rare but robust phenomena, with its strict requirements regarding the electronic environment. The results will help us to identify new electronic structures that can support high-T c superconductivity.

Interatomic Coulomb interaction and electron nematic bond order in FeSe

“…Interestingly, recent neutron scattering experiments in FeSe observed the spin fluctuations around (π, 0) below the structural transition and the magnetic resonance at (π, 0) below the superconducting transition [45,46], which can be explained by the presence of a nematic electronic structure [47]. We also note that the same V -term has been argued recently to play an important role in stabilizing the s-wave pairing symmetry in Fe-based superconductors [44]. The overarching importance of the extended Coulomb interaction V may originate from the lack of the charge reservoir layers and the shorter Fe-Fe bond in bulk FeSe when compared to Fepnictides [23].…”

A possible new family of unconventional high temperature superconductors

“…Theoretical studies have been mainly devoted to explain rich phenomena observed in experiments. After almost three decades of intensive research, it has become extremely clear that if there is any chance to solve the elusive high T c mechanism, a successful theoretical prediction of new high T c materials is necessary.Recently, we suggest that a special electronic trait that separates the two high T c families from other correlated electronic materials is that in both high T c families, those d-orbitals that make the strongest in-plane d-p couplings in the cationanion complexes are isolated near Fermi surface energy [3][4][5] . In magnetically-driven superconducting mechanism, this property makes the effective antiferromagnetic(AFM) superexchange interactions to maximize their contribution to superconducting pairing and simultaneously reduces other unwanted side effects from other orbitals.…”

“…15 by Davis and Lee. The principle provides an unified explanation why the d-wave pairing symmetry and the extended s-wave pairing symmetry are robust respectively in curpates and iron-based superconductors 5 . In the current system, as argued earlier, the AFM exchange couplings are dominated by the NN intra-orbital couplings which can generate NN intra-orbital pairing.…”

Electronic physics and possible superconductivity in layered orthorhombic cobalt oxychalcogenides

“…Enormous research efforts have been devoted to understand their origin of high T c . However, lacking of general principles that can guide us to search for new high T c materials is still the major barrier in reaching a consensus in this field.Recently, we have shown that the two known families of high-T c share a common electronic property-those dorbitals that make the strongest in-plane d-p couplings are isolated near Fermi surface energy [3][4][5]. This special electronic character separates the two families of high T c materials from other correlated electronic materials.…”

“…Recently, we have shown that the two known families of high-T c share a common electronic property-those dorbitals that make the strongest in-plane d-p couplings are isolated near Fermi surface energy [3][4][5]. This special electronic character separates the two families of high T c materials from other correlated electronic materials.…”