Unraveling Enhanced Superconductivity in Single-Layer FeSe through Substrate Surface Terminations

Zou, Qiang; Kim, Gi-Yeop; Kang, Jong-Hoon; Oli, Basu Dev; Ge, Zhuozhi; Weinert, Michael; Mandal, Subhasish; Eom, Chang-Beom; Choi, Si-Young; Li, Lian

doi:10.1021/acs.nanolett.5c01298

Unraveling Enhanced Superconductivity in Single-Layer FeSe through Substrate Surface Terminations

Journal Article · Wed Sep 03 00:00:00 EDT 2025 · Nano Letters

DOI:https://doi.org/10.1021/acs.nanolett.5c01298· OSTI ID:3006778

^[1]; ^[2]; Kang, Jong-Hoon ^[3]; Oli, Basu Dev ^[1]; ^[1]; ^[3]; Mandal, Subhasish ^[1]; Eom, Chang-Beom ^[3]; ^[4]; ^[1]

West Virginia Univ., Morgantown, WV (United States)
Pohang Univ. of Science and Technology (POSTECH) (Korea, Republic of)
Univ. of Wisconsin, Madison, WI (United States)
Pohang Univ. of Science and Technology (POSTECH) (Korea, Republic of); Center for van der Waals Quantum Solids Institute for Basic Science, Pohang (Korea, Republic of)

Single-layer FeSe on SrTiO₃(001) substrates shows a superconducting transition temperature much higher than that of bulk FeSe, which has been attributed to factors such as electron doping, interfacial electron–phonon coupling, and electron correlations. To pinpoint the primary driver, we grew single-layer FeSe films on SrTiO₃(001) substrates with coexisting TiO₂ and SrO surface terminations. Scanning tunneling spectroscopy revealed a larger superconducting gap (17.0 meV) on the TiO₂-termination than on the SrO-termination (10.5 meV). Tunneling spectroscopy also showed a larger work function on the SrO surface, resulting in reduced charge transfer to FeSe, as confirmed by angle-resolved photoemission spectroscopy. Scanning transmission electron microscopy further revealed distinctive interfacial atomic-scale structures, with the Se–Fe–Se tetrahedral angle changing from 109.5° on the SrO-termination to 104.9° on the TiO₂-termination. Compared to dynamical mean field theory calculations, our results indicate that enhanced superconductivity in single-layer FeSe/TiO₂ arises from optimal electron correlations, in addition to sufficient charge transfer from the substrate.

View Accepted Manuscript (DOE)

Research Organization:: West Virginia Univ., Morgantown, WV (United States)

Sponsoring Organization:: USDOE Office of Science (SC), Basic Energy Sciences (BES). Materials Sciences & Engineering Division (MSE)

Grant/Contract Number:: FG02-06ER46327; SC0017632

Other Award/Contract Number:: FA9550-23-1-0498
OAC-1818253
OAC-2311558

OSTI ID:: 3006778

Alternate ID(s):: OSTI ID: 2950741

Journal Information:: Nano Letters, Journal Name: Nano Letters Journal Issue: 47 Vol. 25; ISSN 1530-6992; ISSN 1530-6984

Publisher:: American Chemical SocietyCopyright Statement

Country of Publication:: United States

Language:: English

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