Reentrant Phase Coherence in Superconducting Nanowire Composites

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• 作者：Diane Ansermet ; Alexander P. Petrovi? ; Shikun He ; Dmitri Chernyshov ; Moritz Hoesch ; Diala Salloum ; Patrick Gougeon ; Michel Potel ; Lilia Boeri ; Ole Krogh Andersen ; Christos Panagopoulos
• 刊名：ACS Nano
• 出版年：2016
• 出版时间：January 26, 2016
• 年：2016
• 卷：10
• 期：1
• 页码：515-523
• 全文大小：555K
• ISSN：1936-086X

文摘

The short coherence lengths characteristic of low-dimensional superconductors are associated with usefully high critical fields or temperatures. Unfortunately, such materials are often sensitive to disorder and suffer from phase fluctuations in the superconducting order parameter which diverge with temperature T, magnetic field H, or current I. We propose an approach to overcome synthesis and fluctuation problems: building superconductors from inhomogeneous composites of nanofilaments. Macroscopic crystals of quasi-one-dimensional Na_2?δMo₆Se₆ featuring Na vacancy disorder (δ ≈ 0.2) are shown to behave as percolative networks of superconducting nanowires. Long-range order is established via transverse coupling between individual one-dimensional filaments, yet phase coherence remains unstable to fluctuations and localization in the zero (T,H,I) limit. However, a region of reentrant phase coherence develops upon raising (T,H,I). We attribute this phenomenon to an enhancement of the transverse coupling due to electron delocalization. Our observations of reentrant phase coherence coincide with a peak in the Josephson energy E_J at nonzero (T,H,I), which we estimate using a simple analytical model for a disordered anisotropic superconductor. Na_2?δMo₆Se₆ is therefore a blueprint for a future generation of nanofilamentary superconductors with inbuilt resilience to phase fluctuations at elevated (T,H,I).