Substrate-induced broken C4 symmetry and gap variation in superconducting single-layer FeSe/SrTiO3−(13×13)

Wen Si (司文); Tomoaki Tanaka (田中友晃); Satoru Ichinokura (一ノ倉聖); Toru Hirahara (平原徹)

doi:10.1103/PhysRevB.105.104502

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Substrate-induced broken C4 symmetry and gap variation in superconducting single-layer FeSe/SrTiO3−(13×13)

Wen Si (司文), Tomoaki Tanaka (田中友晃), Satoru Ichinokura (一ノ倉聖), Toru Hirahara (平原徹)

DOI 10.1103/PhysRevB.105.104502 · Physical Review B

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Abstract

We performed scanning tunneling microscopy/spectroscopy (STM/STS) measurements to investigate the superconducting properties of single-layer FeSe grown on SrTiO3 (STO) (001)−(13×13). We found “+” and “z” patterns arranged in 13×13 periodicity in the STM images. Surprisingly, they show C2 symmetry, although free-standing FeSe itself has C4 symmetry. STS spectra and quasiparticle interference patterns near the Fermi level also indicate the broken C4 symmetry with the superconducting gap showing a local variation within the STO surface unit cell because of the short coherence length. This clearly shows the non-negligible role of the substrate surface in the superconductivity of the FeSe/STO system.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
FeSe Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	40	Pressure not reported	onset
FeSe Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	8	Pressure not reported	unknown