A study examines superconductors whose order parameter has several components, showing that the coexistence of these components can break time-reversal symmetry and give rise to an intrinsic Josephson diode effect: supercurrent flows more easily in one direction than the other without the need for an external magnetic field or artificial structures.

The superconducting diode effect has so far been explored mainly in hybrid systems with ferromagnetic layers or under applied field conditions. Here, by contrast, the current asymmetry emerges from the superconducting state itself, when the different order-parameter components combine with a relative phase that violates time reversal. The work examines how this condition shows up in the current-phase relation of the Josephson link.

The key signature is rectification of the supercurrent in the link itself: the critical current in one direction exceeds that in the opposite direction. The magnitude of the effect depends on the coupling between order-parameter components and on their relative phase, opening the door to controlling the diode polarity by tuning intrinsic material parameters rather than external fields.

The results connect with the search for multicomponent superconductors — materials in which the superconducting state is not described by a single scalar order parameter — and with growing interest in dissipationless superconducting devices. An intrinsic Josephson diode could be integrated into superconducting circuits and quantum logic elements without adding magnetic fields or ferromagnetism, simplifying design and reducing sources of decoherence.