Intrinsic interfacial van der Waals monolayers and their effect on the high-temperature superconductor FeSe/SrTiO3

Hunter Sims, Donovan N. Leonard, Axiel Yaël Birenbaum, Zhuozhi Ge, Tom Berlijn, Lian Li, Valentino R. Cooper, Matthew F. Chisholm, Sokrates T. Pantelides

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12 Scopus citations

Abstract

The sensitive dependence of monolayer materials on their environment often gives rise to unexpected properties. It was recently demonstrated that monolayer FeSe on a SrTiO3 substrate exhibits a much higher superconducting critical temperature Tc than the bulk material. Here, we examine the interfacial structure of FeSe/SrTiO3 and the effect of an interfacial Ti1+xO2 layer on the increased Tc using a combination of scanning transmission electron microscopy and density functional theory. We find Ti1+xO2 forms its own quasi-two-dimensional layer, bonding to both the substrate and the FeSe film by van der Waals interactions. The excess Ti in this layer can reconstruct the FeSe Fermi surface in a manner consistent with experimental observations. Moreover, the interfacial layer introduces symmetry-breaking distortions in the FeSe film that may favor a Tc increase. These results suggest that this common substrate may be functionalized to modify the electronic structure of a variety of thin films and monolayers.

Original languageEnglish
Article number144103
JournalPhysical Review B
Volume100
Issue number14
DOIs
StatePublished - Oct 14 2019

Funding

DFT calculations and related analysis were supported by U. S. DOE Grant No. DE-FG02-09ER46554 and the McMinn endowment at Vanderbilt University (H.S. and S.T.P.). They were performed at the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility supported by the Office of Science of the U. S. Department of Energy under Contract No. DE-AC02-05CH11231. Work at ORNL is sponsored by the U. S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division (D.N.L., A.Y.B., T.B., V.R.C., and M.F.C.). Work at West Virginia University (Z.G. and L.L.) is supported by the U. S. National Science Foundation, Division of Materials Research (Grant No. DMR-1335215). H.S. wishes to acknowledge helpful communication with G.-X. Zhang and A. Tkatchenko concerning the application of vdW-TS to pbesol . We also wish to acknowledge useful conversations with T. A. Maier concerning the theory of superconductivity.

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