The interactions between antiferromagnetism, tetrahedral sites and electron-phonon coupling in FeSe1-xTex and FeSe/SrTiO3

TL;DR

This paper models the superconducting transition temperature of FeSe1-xTex and FeSe/SrTiO3, highlighting the roles of antiferromagnetism, lattice vibrations, and interface effects in enhancing Tc, aligning well with experimental data.

Contribution

It introduces a modified McMillan approach that incorporates antiferromagnetism and interfacial effects to accurately predict Tc in FeSe-based superconductors.

Findings

The model predicts Tc values consistent with experimental results under pressure.

Interfacial effects with SrTiO3 significantly increase the estimated Tc.

Enhanced electron-phonon coupling explains high Tc in monolayer FeSe/SrTiO3.

Abstract

We show that the superconducting transition temperature Tc of FeSe1-xTex can be computed to reasonable values in a modified McMillan approach in which the electron-phonon coupling is amplified by the antiferromagnetism and the out-of-plane phonons triggered by the tetrahedral lattice sites. This interplay is not only effective at ambient pressure, but also under hydrostatic compression. According to our model, the theoretical Tc of the compressed FeSe0.5Te0.5 agrees with experiment results. More importantly, by taking into account the interfacial effect between an FeSe monolayer and its SrTiO3 substrate as an additional gain factor, our calculated Tc value is up to 91 K high, and provides evidence that the strong Tc enhancement recently observed in such monolayers with Tc reaching 100 K may be due to an enhanced-electron phonon coupling.