Phonon mechanism explanation of the superconductivity dichotomy between FeSe and FeS monolayers on SrTiO3 and other substrates

2021/02/07 by B. Rosenstein, Baruch Rosenstein, B. Ya. Shapiro · 5 citations
Chemistry · Materials Science · Physics and Astronomy · #Chemistry #Condensed matter physics #Coupling (piping) #Crystallography #Electron #Ion #Ionic bonding #Iron-based superconductors research #Materials science #Phonon #Physics #Quantum mechanics #Rare-earth and actinide compounds #Substrate (aquarium) #Superconductivity #Superconductivity in MgB2 and Alloys #cond-mat.supr-con

paper · pdf · doi:10.1103/physrevb.103.224517

published in Physical review. B./Physical review. B 103(22) (American Physical Society)

arxiv created 2021/02/07 · openalex created_date 2021/02/15 · openalex publication_date 2021/06/14 · arxiv updated 2021/06/23 · openalex updated_date 2026/08/05

Abstract

It was observed recently [Shigekawa et al., PNAS 116, 2470 (2019)] that while monolayer iron chalcigenide FeSe on a SrTiO₃ (STO) substrate has a very high critical temperature, its chemical and structural twin material FeS/STO has a very low T_c, if any. To explain this, the substrate interfacial phonon model of superconductivity in iron chalcogenides is further developed. The main glue is the oxygen ion \mathrm\ensuremathΩ_s=60\phantom\rule0.16em0exmeV vibrations longitudinal optical (LO) mode. The mode propagates mainly in the TiO₂ layer adjacent to the monolayer (and also generally present in similar highly polarized ionic crystals like BaTiO₃, rutile, and anatase). It has stronger electron-phonon coupling to electron gas in FeSe than a well-known \mathrm\ensuremathΩ_h=100\phantom\rule0.16em0exmeV harder LO mode. It is shown that while (taking into account screened Coulomb repulsion effects) the critical temperature of FeSe on STO and TiO₂ is above 65\phantom\rule0.16em0exK, it becomes less than 5\phantom\rule0.16em0exK for FeS due to two factors suppressing the electron-phonon coupling. The effective mass in the latter is twice smaller and, in addition, the distance between the electron gas in FeSe to the vibrating substrate oxygen atoms is 15% smaller than in FeS, reducing the central peak in electron-phonon interaction. The theory is extended to other ionic insulating substrates.

Citations

• Tuning the band structure and superconductivity in single-layer FeSe by interface engineering
• Coexistence of superconductivity and antiferromagnetism in (Li0.8Fe0.2)OHFeSe
• Transition Temperature of Strong-Coupled Superconductors
• Interface induced high temperature superconductivity in single unit-cell FeSe films on SrTiO3
• Multichannel superconductivity of monolayer FeSe on SrTiO3: Interplay of spin fluctuations and electron-phonon interaction
• Origin of the Electronic Structure in Single-Layer FeSe/SrTiO3 Films

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• Light-driven lattice metastability for enhanced superconductivity in FeSe/SrTiO3