Interfacial mode coupling as the origin of the enhancement of Tc in FeSe films on SrTiO3
By J. Lee, F. Schmitt, R. Moore, S. Johnston, Yong-Tao Cui, Wei Li, M. Yi, Zhongkai Liu, M. Hashimoto, Yanfeng Zhang and 4 more. Nature, 2013
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Films of iron selenide (FeSe) one unit cell thick grown on strontium titanate (SrTiO3 or STO) substrates have recently shown superconducting energy gaps opening at temperatures close to the boiling point of liquid nitrogen (77 kelvin), which is a record for the iron-based superconductors. The gap opening temperature usually sets the superconducting transition temperature Tc, as the gap signals the formation of Cooper pairs, the bound electron states responsible for superconductivity. To understand why Cooper pairs form at such high temperatures, we examine the role of the SrTiO3 substrate. Here we report high-resolution angle-resolved photoemission spectroscopy results that reveal an unexpected characteristic of the single-unit-cell FeSe/SrTiO3 system: shake-off bands suggesting the presence of bosonic modes, most probably oxygen optical phonons in SrTiO3 (refs 5, 6, 7), which couple to the FeSe electrons with only a small momentum transfer. Such interfacial coupling assists superconductivity in most channels, including those mediated by spin fluctuations. Our calculations suggest that this coupling is responsible for raising the superconducting gap opening temperature in single-unit-cell FeSe/SrTiO3.
Subfields: Condensed Matter Physics, Electronic, Optical and Magnetic Materials
View Paper: https://www.semanticscholar.org/paper/144444d6b6ef4580165e1bef68245e4ab760743d
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Citations in the corpus
- Plain s-wave superconductivity in single-layer FeSe on SrTiO3 probed by scanning tunnelling microscopy (2015, background): “Scenarios that give the plain s-wave pairing symmetry, should be further examined, including the recent proposed phonon-mediated pairing enhancement scenario [7], the orbital fluctuation mediated pairing [38], and the extended s-wave with a leading cos(kx)cos(ky) paring [12].”
- Angle-resolved photoemission studies of quantum materials (2020, positive): “While nodeless anisotropic gaps are consistently observed in the monolayer system and its bulk counterparts (Du et al., 2018; Lee et al., 2014; Liu et al., 2012; Niu et al., 2015; Zhang et al., 2016c; Zhao et al., 2016), both s- and d-wave symmetry remain viable possibilities as the proposed nodal…”