Self-energy driven resonancelike inelastic neutron spectrum in the s++-wave state in Fe-based superconductors
Abstract
To elucidate the pairing states in Fe-based superconductors, we perform a careful calculation of the dynamical spin susceptibility χS(q ,ω ) at very low temperatures (T ≳1 meV ). The feedback effect on both the self-energy and χS(q ,ω ) from the superconducting gap is self-consistently analyzed based on the fluctuation-exchange (FLEX) approximation. In the s±-wave state, which has sign reversal in the gap function, χS(q ,ω ) at the nesting momentum q =Q shows a resonance peak even when the system is away from the magnetic quantum critical point (QCP). In the s++-wave state that has no sign reversal, χS(q ,ω ) shows a large hump structure when the system is close to the magnetic QCP. This result confirms the validity of a self-energy driven resonancelike peak in the s++-wave state proposed in our previous semimicroscopic study: The enhancement in χS(q ,ω ) due to the self-energy effect exceeds the suppression due to the coherence factor effect near the magnetic QCP. We stress that the hump structure in the s++-wave state given by the FLEX method smoothly changes to a resonancelike sharp peak structure as the system approaches the magnetic QCP, which was not reported in our previous studies. The obtained ω and T dependence of χS(q ,ω ) in the s++-wave states resembles the resonancelike feature in inelastic neutron scattering spectra recently observed in Na(Fe,Co)As and FeSe.
- Publication:
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Physical Review B
- Pub Date:
- October 2018
- DOI:
- 10.1103/PhysRevB.98.165143
- arXiv:
- arXiv:1805.09716
- Bibcode:
- 2018PhRvB..98p5143T
- Keywords:
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- Condensed Matter - Strongly Correlated Electrons;
- Condensed Matter - Superconductivity
- E-Print:
- 11 pages, 14 figures, Apprndix B has been added