Structural transition, ferro-orbital order and its fluctuation-mediated s ++-wave superconductivity in iron pnictides

Yoshiaki Ono, Yuki Yanagi, Naoko Adachi, Youichi Yamakawa

Research output: Contribution to journalArticlepeer-review

7 Citations (Scopus)


We investigate the electronic states and the superconductivity in the two-dimensional 16-band dp model extracted from a tight-binding fit to the band structure of iron pnictides, in the presence of both the Coulomb interaction between Fe d-electrons and the electronlattice coupling g with the orthorhombic mode which is crucial for reproducing the recently observed ultrasonic softening of the elastic constant C66. Due to the cooperative effects of these interactions, the ferro-orbital order with different occupations of dyz and dzx orbitals occurs and induces the tetragonal-orthorhombic structural transition at Ts, together with the stripe-type antiferromagnetic (AFM) order below TN. For a large g case, we obtain the phase diagram consistent with the doped iron pnictides with Ts> TN for x>0, where the s+ +-wave superconductivity is mediated by the ferro-orbital fluctuation which is largely enhanced near the ferro-orbital QCP at xc with Ts→0. On the other hand, for a small g case, the simultaneous phase transition occurs at Ts= TN even for x>0, where the - wave superconductivity is mediated by the AFM fluctuation. Both the s-wave states with full superconducting gaps are consistent with most of the experiments but only the former is considered to account for the small Tc-suppression against nonmagnetic impurities.

Original languageEnglish
Pages (from-to)701-710
Number of pages10
JournalSolid State Communications
Issue number8
Publication statusPublished - 2012 Apr
Externally publishedYes


  • A. Superconductors
  • D. Electronelectron interactions
  • D. Electronphonon interactions
  • D. Phase transitions

ASJC Scopus subject areas

  • Chemistry(all)
  • Condensed Matter Physics
  • Materials Chemistry


Dive into the research topics of 'Structural transition, ferro-orbital order and its fluctuation-mediated s <sub>++</sub>-wave superconductivity in iron pnictides'. Together they form a unique fingerprint.

Cite this