Incommensurate smectic phase in close proximity to the high-Tc superconductor FeSe/SrTiO3

Abstract

Superconductivity is significantly enhanced in monolayer FeSe grown on SrTiO3, but not for multilayer films, in which large strength of nematicity develops. However, the link between the high-transition temperature superconductivity in monolayer and the correlation related nematicity in multilayer FeSe films is not well understood. Here, we use low-temperature scanning tunneling microscopy to study few-layer FeSe thin films grown by molecular beam epitaxy. We observe an incommensurate long-range smectic phase, which solely appears in bilayer FeSe films. The smectic order still locally exists and gradually fades away with increasing film thickness, while it suddenly vanishes in monolayer FeSe, indicative of an abrupt smectic phase transition. Surface alkali-metal doping can suppress the smectic phase and induce high-Tc superconductivity in bilayer FeSe. Our observations provide evidence that the monolayer FeSe is in close proximity to the smectic phase, and its superconductivity is likely enhanced by this electronic instability as well.

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• Unconventional density waves and superconductivities in Fe-based superconductors and other strongly correlated electron systems
• Electronic Stripe Patterns Near the Fermi Level of Tetragonal Fe(Se,S)
• Checkerboard order state in superconducting FeSe/SrTiO3(001) monolayer
• Ubiquitous stripe phase and enhanced electron pairing in interfacial high-Tc superconductor FeSe/BaTiO${}_3$
• Defect-induced electronic smectic state at the surface of nematic materials
• Rotation of the dislocation grid in multilayer FeSe films and visualization of electronic nematic domains via orbital-selective tunneling
• Sublattice Dichotomy in Monolayer FeSe Superconductor
• Valley polarization of Landau levels driven by residual strain in the ZrSiS surface band
• Suppression and revival of superconducting phase coherence in monolayer FeSe/SrTiO${}_3$
• Coexisting electronic smectic liquid crystal and superconductivity in a Si square-net semimetal
• Dual Enhancement of Superconductivity in FeSe/SrTiO3 via Orbital and Correlation Synergy