The superconducting diode effect, characterized by direction-dependent critical supercurrents, has attracted considerable attention for its potential applications in low-dissipation and quantum electronic devices. In this seminar, I will discuss how nonreciprocal supercurrents can be generated and controlled through two complementary approaches: intrinsic crystal symmetry and interfacial proximity engineering.

First, I will present an intrinsic Josephson diode effect in vertical van der Waals junctions incorporating non-centrosymmetric T_d-WTe₂ barriers. The broken inversion symmetry and polar crystal structure of WTe₂, combined with time-reversal-symmetry breaking by an in-plane magnetic field, generate magneto-chiral nonreciprocal supercurrents. Systematic measurements of the magnetic-field orientation, barrier thickness, and temperature reveal that the diode response is closely linked to the crystal symmetry of WTe₂ and distinguish it from extrinsic geometric or vortex-related effects. I will then discuss exchange-spin-split Josephson junctions based on proximity-magnetized Pt, Ta, W, and Pd layers. Superconducting quantum interferometry provides direct evidence of a nonvolatile anomalous phase shift, φ₀, associated with spontaneous time-reversal-symmetry breaking. A comparison among different proximity layers further demonstrates that the magnitude and polarity of the zero-field diode effect cannot be determined by the spin Hall response alone. Instead, they emerge from the combined influence of interfacial magnetic ordering, exchange spin splitting, and Rashba spin–orbit interaction.

Together, these results illustrate a progression from identifying crystal-symmetry-driven superconducting nonreciprocity to engineering its phase, polarity, and magnitude through interfacial proximity effects, offering a pathway toward field-free superconducting phase and rectifying devices.