Microscopic mechanism of enhanced superconductivity in FeSe/SrTiO3

Determine the microscopic mechanism responsible for the enhanced superconducting transition temperature in single-unit-cell FeSe films grown on SrTiO3(100), including the respective roles of substrate-to-film charge transfer, interfacial electron–phonon coupling, and suppression of spin-density waves.

Background

Single-unit-cell FeSe films on SrTiO3(100) exhibit superconducting signatures at temperatures substantially above the bulk FeSe transition temperature. The paper identifies several possible contributing mechanisms, including charge transfer from the substrate, enhanced electron–phonon coupling across the interface, and quenching of spin-density waves.

The authors explicitly state that the microscopic origin of this enhancement has not been fully established. This unresolved mechanism is important for understanding and controlling superconductivity in thicker FeSe films and related heterostructures.

References

Although the microscopic mechanism responsible for the enhanced Tc is not entirely understood, there is consensus that it likely arises from charge transfer from the substrate into the ultra-thin FeSe film, accompanied by enhanced electron-phonon coupling across the interface[19,21,22] and possibly the quenching of spin density waves in the interfacial FeSe region.[23]

— Enhanced Superconductivity in Multilayer FeSe Films by Simplified Molecular Beam Epitaxy  (2608.24710 - Hilse et al., 25 Aug 2026) in Section 1, Introduction

The nature of superconductivity in multi-UC FeSe films on SrTiO3(100) presents an unresolved puzzle of particular interest in this context.

— Enhanced Superconductivity in Multilayer FeSe Films by Simplified Molecular Beam Epitaxy  (2608.24710 - Hilse et al., 25 Aug 2026) in Section 1, Introduction; Section 2.4, Microstructure and electronic properties of optimized multilayer β-FeSe films