Picosecond pulses push superconductors past their critical-current limit

Overview

Updated 2 hours ago

The intrinsic current limit of a superconductor — the point where Cooper pairs tear apart — has been known theoretically for decades but never measured directly. Vortex motion and self-heating always destroyed the supercurrent first. A team at the Max Planck Institute for the Structure and Dynamics of Matter in Hamburg has now bypassed both by firing picosecond electrical pulses, far too short for vortices to move.

The study, published in Nature Physics on 24 September 2026, is the first direct transport measurement of the depairing current density in a type-II superconductor. It also offers a way to probe a material's superconducting gap symmetry and a path toward devices running near their true current limit.

Why it matters

Superconducting cables and magnets could carry more than twice today's current once devices run near the intrinsic limit this method exposed.

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Key Indicators

2.2×

NbN depairing current vs. DC critical current

Picosecond pulses drove NbN to 2.2 times its DC critical current density before depairing began.

≈100 GA m⁻²

NbN DC critical current density at 7 K

Baseline vortex-limited critical current measured by conventional DC transport.

≈50 GA m⁻²

YBCO DC critical current density at 50 K

Baseline for the d-wave material, the second superconductor tested in the study.

300 fs

Laser pulse width driving the switches

Photoconductive switches fired by green laser pulses generate the few-picosecond current pulses.

Voices

Curated perspectives — historical figures and your fellow readers.

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People Involved

Andrea Cavalleri

Research group leader, Max Planck Institute for the Structure and Dynamics of Matter

Led the study; directs the MPSD group in Hamburg

Guido Meier

Co-author, Max Planck Institute for the Structure and Dynamics of Matter

Developed the ultrafast electrical-transport platform used in the study

Organizations Involved

Max Planck Institute for the Structure and Dynamics of Matter (MPSD)

Research institute

Conducted and led the study

The Hamburg institute where the picosecond transport platform was developed and the experiments ran.

Nature Physics

Peer-reviewed scientific journal

Published the study as open access

Monthly peer-reviewed journal published by Springer Nature that carried the picosecond depairing study.

Timeline

March 2026 September 2026

2 events Latest: 2 days ago

September 2026
Nature Physics publishes picosecond depairing study
Latest Publication

The journal reports that picosecond pulses drive NbN and YBCO supercurrents to the intrinsic depairing limit, bypassing vortex motion and self-heating.
2 days ago
March 2026
Preprint posted to arXiv
Research

The MPSD team posted its results to arXiv (identifier 2603.24711) before the Nature Physics publication later that year.
March 2026

Scenarios

Picosecond depairing extends to more superconductor families

Possible Resolves by End of 2027

Discussed by: The Nature Physics authors and MPSD press materials, who note broader measurements are needed to test how generally the result applies

If the method works on materials with other gap symmetries — iron-based superconductors, multi-gap materials, disordered films — it becomes a standard tool for probing intrinsic current limits across the field. The MPSD team explicitly called for these follow-up measurements.

Method settles a contested gap symmetry

Uncertain Resolves by End of 2028

Discussed by: Andrea Cavalleri, who said picosecond transport can access gap symmetry that DC transport cannot

The claim that picosecond depairing reveals gap symmetry could be tested on a material whose pairing is debated, such as certain nickelates. If the method determines the symmetry of such a material, it becomes a meaningful new probe for strongly correlated systems.

Results face replication trouble or a competing explanation

Unlikely Resolves by End of 2028

Discussed by: The paper's own extended discussion ruling out depinned vortices, suggesting the interpretation will be scrutinized

The interpretation rests on vortices being inertially frozen on picosecond timescales. If another lab fails to reproduce the result, or a critique emerges arguing vortex or phase-slip contributions matter even on these timescales, the generality of the finding weakens.

Historical Context

2 moments from history that rhyme with this story — and how they unfolded.

1957

BCS theory (1957)

Bardeen, Cooper and Schrieffer published the microscopic theory of superconductivity, showing that Cooper pairs carry supercurrent. The theory implied a fundamental limit — the depairing current — beyond which pairs break apart into normal carriers.

Then

BCS theory explained most conventional superconductors and won the 1960 Nobel Prize in Physics.

Now

The depairing current remained a theoretical benchmark that real type-II materials never reached, because vortices and heating always caused failure at lower currents.

Why this matters now

This experiment is the first direct transport measurement to reach the depairing limit BCS theory and its successors predicted decades ago.

January 1987

YBa₂Cu₃O₇ discovery (1987)

Wu, Chu and colleagues at the University of Houston and University of Alabama found a copper-oxide compound superconducts above 90 K, above liquid nitrogen temperature, igniting a global race to understand high-temperature superconductors.

Then

YBCO became the most intensively studied high-temperature superconductor in the world.

Now

Angle-resolved photoemission experiments later confirmed its d-wave pairing symmetry, with a gap that vanishes along certain momentum directions.

Why this matters now

YBCO is the d-wave material in this study; its momentum-dependent gap is exactly why the team saw gradual, threshold-free depairing instead of the sharp transition measured in s-wave NbN.