Fermi Surface and Mass Renormalization in the Iron-Based Superconductor YFe_{2}Ge_{2}.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Superconductivity

Background:

• Interaction-enhanced carrier masses are crucial for understanding iron-based superconductors.
• Unconventional superconductors exhibit complex electronic properties requiring detailed investigation.

Purpose of the Study:

• To investigate the electronic structure and carrier masses of the novel iron-based superconductor YFe2Ge2.
• To correlate the observed carrier masses with the material's heat capacity properties.

Main Methods:

• Utilized quantum oscillation measurements to probe the Fermi surface.
• Analyzed band structure calculations to identify electronic pockets.
• Measured the heat capacity to determine the Sommerfeld coefficient.

Main Results:

• Resolved all four predicted Fermi surface pockets (one electron, three hole).
• Observed exceptionally high carrier masses, up to 20 times the bare electron mass.
• Determined a high Sommerfeld coefficient (≃100 mJ/mol K²), consistent with enhanced masses.

Conclusions:

• The high carrier masses in YFe2Ge2 are among the largest in iron-based superconductors.
• Uniform mass renormalization suggests local correlations, potentially indicative of a Hund's metal scenario.