Superconductivity on the Verge of a Pressure-Induced Lifshitz Transition in CaFe{sub 2}As{sub 2}: an Interpretation Within the Eliashberg Theory
- Politecnico di Torino, Dipartimento di Scienza Applicata e Tecnologia (Italy)
In a recent paper, we presented the first directional point-contact Andreev reflection spectroscopy (PCARS) measurements on CaFe{sub 2}As{sub 2} crystals under quasi-hydrostatic pressure and discussed the pressure dependence of the gaps and the critical temperature. While T{sub c} exhibits a well-known smooth dependence and a broad maximum at about 0.6 GPa, both gaps increase very sharply in a small pressure range between 0.5 and 0.6 GPa, leading to a doubling of the ratio 2Δ{sub 2}/k{sub B}T{sub c} and a quadruplication of the ratio 2Δ{sub 1}/k{sub B}T{sub c}, Δ{sub 1} and Δ{sub 2} being the small and large gap, respectively. This peculiar behavior is likely to be related to a sharp change in the lattice structure that, in turn, produces a 2D-3D topological transition in the hole-like Fermi surface sheet. In this work, we show that, within an effective three-band Eliashberg theory for the electron-spin fluctuation coupling (s± symmetry), these results can be rationalized as being due to a large increase of the electron-boson coupling, which mimics the effects of a boost mechanism for the coupling related to the underlying Lifshitz transition.
- OSTI ID:
- 22777036
- Journal Information:
- Journal of Superconductivity and Novel Magnetism, Vol. 31, Issue 3; Other Information: Copyright (c) 2018 Springer Science+Business Media, LLC, part of Springer Nature; Article Copyright (c) 2017 Springer Science+Business Media, LLC; http://www.springer-ny.com; Country of input: International Atomic Energy Agency (IAEA); ISSN 1557-1939
- Country of Publication:
- United States
- Language:
- English
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