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Anomalous critical fields in quantum critical superconductors.

Putzke, C*; Walmsley, P*; Fletcher, J D; Malone, L*; Vignolles, D*; Proust, C*; Badoux, S*; See, P; Beere, H E*; Ritchie, D A*; Kasahara, S*; Mizukami, Y*; Shibauchi, T*; Matsuda, Y*; Carrington, A* (2014) Anomalous critical fields in quantum critical superconductors. Nature Comms., 5. p. 5679.

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Fluctuations around an antiferromagnetic quantum critical point (QCP) are believed to lead to unconventional superconductivity and in some cases to high-temperature superconductivity. However, the exact mechanism by which this occurs remains poorly understood. The iron-pnictide superconductor BaFe2(As1-xPx)2 is perhaps the clearest example to date of a high-temperature quantum critical superconductor, and so it is a particularly suitable system to study how the quantum critical fluctuations affect the superconducting state. Here we show that the proximity of the QCP yields unexpected anomalies in the superconducting critical fields. We find that both the lower and upper critical fields do not follow the behaviour, predicted by conventional theory, resulting from the observed mass enhancement near the QCP. Our results imply that the energy of superconducting vortices is enhanced, possibly due to a microscopic mixing of antiferromagnetism and superconductivity, suggesting that a highly unusual vortex state is realized in quantum critical superconductors.

Item Type: Article
Keywords: superconductivity
Subjects: Quantum Phenomena
Quantum Phenomena > Nanophysics
Identification number/DOI: 10.1038/ncomms6679
Last Modified: 02 Feb 2018 13:14
URI: http://eprintspublications.npl.co.uk/id/eprint/6515

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