Bandwidth and Electron Correlation-Tuned Superconductivity in Rb_{0.8}Fe_{2}(Se_{1-z}S_{z})_{2}

Area of Science:

• Condensed Matter Physics
• Materials Science
• Solid State Chemistry

Background:

• Iron chalcogenides exhibit complex electronic properties, including superconductivity.
• Tuning electronic structure is crucial for understanding and optimizing superconductivity in these materials.

Purpose of the Study:

• To investigate the impact of sulfur-selenium substitution on the electronic structure of Rb_{0.8}Fe_{2}(Se_{1-z}S_{z})_{2}.
• To identify the key factors governing the suppression of superconductivity and the emergence of metallic behavior.

Main Methods:

• Systematic angle-resolved photoemission spectroscopy (ARPES) was employed.
• The study focused on the series Rb_{0.8}Fe_{2}(Se_{1-z}S_{z})_{2} with varying sulfur content (z=0, 0.5, 1).

Main Results:

• Little change in Fermi surface topology was observed across the substitution series.
• A significant reduction in overall bandwidth (by a factor of 2) was noted when moving from Rb_{0.8}Fe_{2}S_{2} to Rb_{0.8}Fe_{2}Se_{2}.
• Superconductivity was suppressed into a metallic phase with increasing sulfur content.

Conclusions:

• Electron correlation, manifested in quasiparticle bandwidth, is identified as the critical tuning parameter for superconductivity in these iron chalcogenides.
• Moderate electron correlation is essential for achieving high critical temperatures (T_{C}).