Abstract
In the family of the iron-based superconductors, the REFeAsO-type compounds (with RE being a rare-earth metal) exhibit the highest bulk superconducting transition temperatures (Tc) up to 55 K and thus hold the key to the elusive pairing mechanism. Recently, it has been demonstrated that the intrinsic electronic structure of SmFe0.92Co0.08AsO (Tc = 18 K) is highly nontrivial and consists of multiple band-edge singularities in close proximity to the Fermi level. However, it remains unclear whether these singularities are generic to the REFeAsO-type materials and if so, whether their exact topology is responsible for the aforementioned record Tc. In this work, we use angle-resolved photoemission spectroscopy (ARPES) to investigate the inherent electronic structure of the NdFeAsO0.6F0.4 compound with a twice higher Tc = 38 K. We find a similarly singular Fermi surface and further demonstrate that the dramatic enhancement of superconductivity in this compound correlates closely with the fine-tuning of one of the band-edge singularities to within a fraction of the superconducting energy gap Δ below the Fermi level. Our results provide compelling evidence that the band-structure singularities near the Fermi level in the iron-based superconductors must be explicitly accounted for in any attempt to understand the mechanism of superconducting pairing in these materials.
Highlights
In the family of the iron-based superconductors, the REFeAsO-type compounds exhibit the highest bulk superconducting transition temperatures (Tc) up to 55 K and hold the key to the elusive pairing mechanism
The observation of the Fermi-surface topology drastically different from the early predictions of the ab initio calculations in some compounds[1,2,3,4] has cast doubt on the theoretical description of superconductivity based on this simplified picture and necessitates the adoption of the true Fermi surface, a paradigm shift that is beginning to occur[5,6]
Recent observation of a highly nontrivial electronic structure in SmFe0.92Co0.08AsO shaped by multiple band-edge singularities in the vicinity of the Fermi level (EF) implies, should it prove to be generic for the 1111-type compounds, that very small changes on the order of tens of meV can potentially lead to drastic changes in the Fermi-surface topology and strongly affect the superconducting state
Summary
In the family of the iron-based superconductors, the REFeAsO-type compounds (with RE being a rare-earth metal) exhibit the highest bulk superconducting transition temperatures (Tc) up to 55 K and hold the key to the elusive pairing mechanism. It indicates that albeit the hole bands giving rise to the blades of the propellerlike structure in the intensity maps in Fig. 1a,b (integrated in a window of ± 15 meV around the Fermi level) terminate in the immediate vicinity of the Fermi level, they do not cross it and, do not contribute to the Fermi surface of NdFeAsO0.6F0.4.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
