Synopsis: Spin-triplet supercurrents in a magnetic Josephson junction

With a clever design of a ferromagnetic Josephson junction, it is possible to observe a theoretically predicted, but difficult to measure, spin-triplet supercurrent.
Synopsis figure
Illustration: Courtesy of N. Birge

If a conventional superconductor is brought into contact with a normal metal, superconducting pair correlations penetrate into the metal, a process known as the superconducting proximity effect. If the metal is instead ferromagnetic, the penetration of superconducting pairs, which typically form spin-singlets, is much shorter. Theoretically, however, if the ferromagnet is inhomogeneous, then spin-triplet electron pairs would appear at the superconductor-ferromagnet interface that could penetrate further into the ferromagnet.

In a paper appearing in Physical Review Letters, Trupti Khaire, Mazin Khasawneh, William Pratt, Jr., and Norman Birge of Michigan State University in the US have constructed an ingenious superconductor-ferromagnet-superconductor Josephson junction to look for such a spin-triplet current. Their trick is to construct the ferromagnetic layer from a multilayered sandwich of weak and strong transition-metal magnetic layers. The complicated magnetic layer is necessary to create a noncollinear magnetic environment for the Cooper pairs from the superconductor, which is required to generate the spin-triplet pairs. The layer also suppresses the spin-singlet supercurrent, thereby making the spin-triplet current easier to detect. Khaire et al. find a spin-triplet supercurrent that depends on magnetic layer thickness, and persists for at least several tens of nanometers. – Daniel Ucko


More Announcements »

Subject Areas


Previous Synopsis

Atomic and Molecular Physics

Something magic in the alkalis

Read More »

Next Synopsis

Soft Matter

Entangled in tubes

Read More »

Related Articles

Focus: Detecting Photons With a Thermometer

Focus: Detecting Photons With a Thermometer

A new technique detects as few as 200 microwave photons at a time by the heat they supply to an electrical circuit. Read More »

Synopsis: How Spin Waves Bend

Synopsis: How Spin Waves Bend

Researchers have verified experimentally that the reflection and refraction of spin waves at an interface follow a Snell’s-like law. Read More »

Synopsis: Polarons Drive a Magneto-Optical Effect

Synopsis: Polarons Drive a Magneto-Optical Effect

A surprisingly large magneto-optical response occurs when mobile electrons in a cooled material become trapped by their interaction with the surrounding lattice. Read More »

More Articles