Giant Noise in a Superconductor-Magnet Sandwich ⚡ экспресс
Shot-noise measurements in superconductor/insulator/ferromagnet junctions (V/MgO/Fe) revealed a colossal enhancement—several orders of magnitude above expectations. The origin lies in a peculiar realization of the superconducting proximity effect, steered by orbital symmetries. Inversion-symmetry breaking within the heterostructure and the emergent interfacial spin-orbit coupling give rise to triplet superconductivity in ferromagnetic iron, which starkly contrasts with the singlet superconductivity of vanadium. Thus, it has been experimentally shown that the enhanced shot noise, typical of Josephson junctions with two superconductors, can also manifest in a single-superconductor system. This finding compels a reexamination of spin-orbit interactions and proximity effects across a broad material landscape.
Ordinary electrical noise is like a faint hiss in headphones. This is shot noise from electrons passing through a contact. But in the experiment with a sandwich of superconducting vanadium, MgO insulator, and magnetic iron, this noise roared, becoming hundreds of times louder.
The secret lies in the proximity effect: a superconductor "infects" neighboring layers with its ability to conduct current without resistance. Conventional superconductivity was explained by John Bardeen, and Leo Esaki studied tunneling effects. Usually, electrons in a superconductor form pairs with opposite spins—like two dancers spinning in opposite directions. But in this sandwich, the spins aligned in the same direction, as if both are spinning to the right. This is triplet superconductivity. It allowed current to flow unimpeded through the magnetic iron, generating giant noise.
This discovery changes the physics of layered structures and paves the way for spintronics—electronics that uses electron spin instead of charge.
🎯 Iron, normally a magnet, in this structure temporarily turns into a superconductor—current flows without resistance through it.