Effects of Chemical Pressure on Superconductivity in Electrochemically Intercalated (TMA)yFe2(Se1-xSx)2 (TMA = Tetramethylammonium)

TL;DR

This study investigates how chemical pressure, via sulfur substitution and intercalation with TMA+, influences superconductivity in FeSe-based materials, revealing a linear decrease in Tc and unit cell volume with sulfur content and similar effects of chemical pressure and electron doping.

Contribution

It demonstrates that chemical pressure affects intercalated and host FeSe compounds similarly, providing new insights into tuning superconductivity through chemical modifications.

Findings

Tc decreases linearly with sulfur content

Unit cell volume decreases linearly with sulfur content

Chemical pressure impacts intercalated and host compounds similarly

Abstract

The beta-modification of FeSe, which has an anti-PbO type structure, achieves superconductivity at 8 K without external doping or pressure and exhibits a nematic phase, which has been crucial for studies of unconventional pairing mechanisms. Although the critical temperature (Tc) in FeSe increases significantly with applied pressure, intercalation, and in thin films, the effect of replacing selenium with sulfur in FeSe1-xSx has remained unclear. To investigate the effects of chemical pressure, we have synthesized FeSe1-xSx crystals (up to x = 0.52) and intercalated them with tetramethylammonium ions (TMA+). Our results show that both Tc and unit cell volume decrease linearly with sulfur content in both host and intercalated (TMA)yFe2(Se1-xSx)2. The unexpected common rate of normalized decrease of Tc suggests that chemical pressure affects the electron-doped intercalates in the same way as the host compounds. This result highlights the unique role of chemical pressure and electron doping in tuning superconductivity in FeSe systems and provides new insights into their complex behavior.