The enhanced superconductivity in monolayer FeSe on titanates opens a fascinating pathway toward the rational design of high-temperature superconductors. Utilizing the state-of-the-art oxide plus chalcogenide molecular beam epitaxy systems connected to a synchrotron angle-resolved photoemission spectroscope, epitaxial LaTiO layers with varied atomic thicknesses are inserted between monolayer FeSe and SrTiO, for systematic modulation of interfacial chemical potential. With the dramatic increase of electron accumulation at the LaTiO/SrTiO surface, providing a substantial surge of work function mismatch across the FeSe/oxide interface, the charge transfer and the superconducting gap in the monolayer FeSe are found to remain markedly robust. This unexpected finding indicate the existence of an intrinsically anchored "magic" doping within the monolayer FeSe systems.
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http://dx.doi.org/10.1002/advs.202003454 | DOI Listing |
Nano Lett
December 2024
State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China.
Two-dimensional (2D) superconductors that reside on substrates must be influenced by Rashba spin-orbit coupling (SOC). The intriguing effect of Rashba-type SOCs on iron-based superconductors (IBSs) has remained largely a mystery. In this work, we unveil modified Landau-level spectroscopy and the intricate band splitting of FeSe monolayers through the precision of scanning tunneling spectroscopy, which unequivocally demonstrates the presence of Rashba SOC.
View Article and Find Full Text PDFPhys Rev Lett
June 2024
Department of Materials Science and Engineering, University of Delaware, Newark, Delaware 19716, USA.
We undertook a comprehensive investigation of the electronic structure of FeSe, known as a Hund metal, and found that it is not uniquely defined. Through accounting for all two-particle irreducible diagrams constructed from electron Green's function G and screened Coulomb interaction W in a self-consistent manner, a Mott-insulator phase of 2D-FeSe is unveiled. The metal-insulator transition is driven by the strong on-site Coulomb interaction in its paramagnetic phase, accompanied by the weakening of both local and nonlocal screening effects on the Fe-3d orbitals.
View Article and Find Full Text PDFNano Lett
July 2024
Department of Physics, University of California, Berkeley, California 94720, United States.
Polymorph engineering involves the manipulation of material properties through controlled structural modification and is a candidate technique for creating unique two-dimensional transition metal dichalcogenide (TMDC) nanodevices. Despite its promise, polymorph engineering of magnetic TMDC monolayers has not yet been demonstrated. Here we grow FeSe monolayers via molecular beam epitaxy and find that they have great promise for magnetic polymorph engineering.
View Article and Find Full Text PDFACS Nano
July 2024
State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China.
The discovery of high-mobility two-dimensional electron gas and low carrier density superconductivity in multiple SrTiO-based heterostructures has stimulated intense interest in the surface properties of SrTiO. The recent discovery of high- superconductivity in the monolayer FeSe/SrTiO led to the upsurge and underscored the atomic precision probe of the surface structure. By performing atomically resolved cryogenic scanning tunneling microscopy/spectroscopy characterization on dual-TiO-terminated SrTiO(001) surfaces with (√13 × √13), c(4 × 2), mixed (2 × 1), and (2 × 2) reconstructions, we disclosed universally broken rotational symmetry and contrasting bias- and temperature-dependent electronic states for apical and equatorial oxygen sites.
View Article and Find Full Text PDFNano Lett
July 2024
Laboratory of Advanced Materials, State Key Laboratory of Surface Physics, and Department of Physics, Fudan University, Shanghai 200438, China.
The discovery of interfacial superconductivity in monolayer FeSe/oxides has spurred intensive research interest. Here we not only extend the FeSe/FeO superconducting interface to FeSe/NdFeO but also establish robust interface-enhanced superconductivity at a very low doping level. Specifically, well-annealed FeSe/NdFeO exhibits a low doping level of 0.
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