Interaction-induced singular Fermi surface in a high-temperature oxypnictide superconductor

Area of Science:

• Condensed Matter Physics
• Materials Science
• Superconductivity

Background:

• LaFeAsO-type materials are iron-based superconductors with high transition temperatures.
• Their electronic structure was predicted to feature large, nested circular Fermi surfaces, enhancing superconductivity.
• This model has been widely accepted for iron-based superconductors.

Purpose of the Study:

• To investigate the Fermi surface electronic structure of a prototypical 1111-type iron-based superconductor, SmFe(0.92)Co(0.08)AsO.
• To challenge the prevailing model of circular Fermi surfaces in iron-based superconductors.
• To explore the relationship between Fermi surface topology and superconducting transition temperature.

Main Methods:

• Theoretical analysis of the electronic structure of SmFe(0.92)Co(0.08)AsO.
• Comparison of the calculated Fermi surface with existing models and experimental data.
• Correlation analysis between Fermi surface features and superconducting properties.

Main Results:

• The Fermi surface of SmFe(0.92)Co(0.08)AsO deviates significantly from the expected circular topology.
• It consists of two unique singular constructs formed by band edges pulled to the Fermi level.
• These singularities influence the low-energy electronic properties and superconductivity.

Conclusions:

• The traditional model of circular Fermi surfaces is not universally applicable to all iron-based superconductors.
• Unique band edge singularities play a crucial role in determining the electronic properties and superconductivity.
• The occurrence of these singularities correlates with the maximum achievable superconducting transition temperature across different iron-based superconductor classes.