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: Supersensitive Needle Magnetometer

Focus: Supersensitive Needle Magnetometer

A tiny, needle-shaped ferromagnet could form a magnetic sensor far better than the current best instruments, according to theory.   Read More »

Viewpoint: A Tale of Two Domes
Condensed Matter Physics

Viewpoint: A Tale of Two Domes

Iron selenide films peppered with potassium atoms exhibit a high-temperature superconducting phase that emerges separately from a low-temperature superconducting phase. Read More »

Synopsis: Even-Handed Control of Quantum Dot Qubits
Quantum Information

Synopsis: Even-Handed Control of Quantum Dot Qubits

A new way to control the coupling of spins between adjacent quantum dots produces qubits that are less susceptible to electronic noise. Read More »

More Articles