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Published on: August 2, 2019
Geometry-driven dimensional crossover from weak localization to superconducting fluctuations in nanostructured NbN
Priyank Tripathi1,2, Debashree Nayak3, Mandeep Kaur1,2
1Academy of Scientific and Innovative Research (AcSIR), Ghaziabad-201002, India. husalesc.nplindia@csir.res.in.
Nanoscale
|June 16, 2026
Summary
Researchers explored how nanofabrication affects superconducting coherence in niobium nitride (NbN) thin films. They found that weak-link spacing, not film thickness, controls quantum transport, enabling geometry-tuned quantum interference effects.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Nanotechnology
Background:
- Nanofabrication of disordered superconductors enables multichannel electron and Cooper-pair transport, crucial for achieving global phase coherence.
- In nanostructured superconductors, transport is governed by weak-link geometry rather than film thickness, with weak-link spacing becoming the critical length scale.
- Confining electron motion to dimensions smaller than film thickness highlights the importance of geometric features in dictating quantum transport.
Purpose of the Study:
- To investigate the recovery of superconducting coherence in niobium nitride (NbN) thin films patterned into nanostructures.
- To analyze how focused ion beam (FIB) milling affects quantum transport phenomena like weak localization (WL) and superconducting fluctuations (SCF).
- To demonstrate geometry-controlled tuning of quantum interference and fluctuation phenomena in disordered superconductors.
Main Methods:
- Focused Ion Beam (FIB) milling was used to pattern NbN thin films into hexagonal arrays of nanoholes.
- Transport behavior was studied under varying magnetic field and temperature conditions.
- Analysis focused on the interplay between weak localization (WL) and superconducting fluctuations (SCF) as a function of temperature.
Main Results:
- Superconducting coherence recovery was observed in NbN films with specific weak-link spacing (∼81 nm).
- Quantum interference-driven weak localization (WL) coexists with superconducting fluctuations (SCF) at a crossover temperature (Tpeak = 12.9 K).
- Superconducting fluctuations (SCF) suppress weak localization (WL) below Tpeak, indicating geometry-driven crossover phenomena.
Conclusions:
- Weak-link spacing is the primary determinant of electron, quasiparticle, and Cooper-pair dynamics in these nanostructured superconductors.
- A geometry-controlled crossover between WL and SCF, analogous to 2D systems, was revealed.
- This work provides a platform for controlling quantum phenomena and developing advanced quantum-coherent devices.
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