Reentrant Phase Coherence in Superconducting Nanowire Composites.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Superconductivity

Background:

• Low-dimensional superconductors possess short coherence lengths, leading to high critical fields/temperatures.
• These materials are susceptible to disorder and phase fluctuations, limiting their practical applications.

Purpose of the Study:

• To investigate the potential of inhomogeneous nanofilamentary composites to overcome synthesis and fluctuation challenges in superconductors.
• To explore the superconducting properties of quasi-one-dimensional Na2-δMo6Se6 crystals with Na vacancy disorder.

Main Methods:

• Fabrication and characterization of macroscopic Na2-δMo6Se6 crystals with controlled Na vacancy disorder (δ ≈ 0.2).
• Analysis of the material's behavior as a percolative network of superconducting nanowires.
• Estimation of Josephson energy (EJ) using a model for disordered anisotropic superconductors.

Main Results:

• Na2-δMo6Se6 crystals exhibit properties of percolative superconducting nanowire networks.
• Phase coherence is initially unstable but shows reentrant behavior upon increasing temperature, magnetic field, or current.
• Reentrant phase coherence is attributed to enhanced transverse coupling via electron delocalization.

Conclusions:

• Na2-δMo6Se6 demonstrates a novel reentrant phase coherence phenomenon in nanofilamentary superconductors.
• This material serves as a blueprint for developing robust superconductors resilient to phase fluctuations at elevated operational parameters.
• The findings suggest a pathway towards next-generation superconducting devices with improved stability.