ArXiv · 2026
The interplay of superconductivity and magnetism gives rise to rich phenomena in Josephson junctions. In this Letter, we study Josephson junctions formed by conventional s-wave superconductors and a PT-symmetric collinear antiferromagnet modeled on CuMnAs. Using microscopic modeling and symmetry analysis, we show that these junctions exhibit both the Josephson diode effect and ϕ₀-junction states. Remarkably, both effects are controlled by the Néel vector: rotating it by 90^∘ switches off both, while reversing it switches the diode polarity. To reveal the microscopic mechanism, we develop a channel-resolved scattering theory that accurately captures the anomalous phases and establishes the exact condition for the diode effect. The interplay of the channel current-phase relations yields a sizable diode efficiency, tunable by both the magnitude and direction of the exchange field. Furthermore, a Green-function reduction identifies a single renormalized PT-degenerate band as the transport carrier and precisely reproduces the full current amplitudes. Our work establishes PT-symmetric antiferromagnets as versatile platforms for field-free, highly tunable Josephson diodes and ϕ₀ junctions.
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