The superconducting diode effect in Josephson junctions fabricated from a structurally chiral superconductor

The superconducting diode effect occurs in superconducting materials in which both time-reversal and inversion symmetry are broken. The recently observed chirality-induced spin selectivity effect demonstrates that chiral materials break both symmetries. Thus, a Josephson junction interface with the left-handed structure on one side of the junction and the right-handed structure on the other should exhibit a diode effect. Here, we report the electrical transport properties of right-handed/left-handed and right-handed/right-handed devices fabricated from single crystals of the structurally chiral superconductor Mo3Al2C. Fraunhofer-like magnetic diffraction patterns confirm the presence of the Josephson effect in all but one of our devices. A magnetic-field-induced superconducting diode effect is demonstrated in the right-handed/left-handed devices by a statistically significant difference in Ic+ and ∣Ic−∣, with a maximum asymmetry of 5%. The intrinsic superconducting diode effect is not observed in the right-handed/right-handed devices. We provide an explanation for the presence of the superconducting diode effect in the right-handed/left-handed devices. The superconducting diode effect describes the non-reciprocal transport behavior of the superconducting current and certain symmetry requirements must be met to realize this phenomenon in a given system. Here, the authors conduct electrical transport measurements on bi-crystal Josephson junctions (JJs) made from the chiral superconductor Mo3Al2C where each junction either has the same or opposite structural chirality. Under an applied magnetic field, they observe the diode effect for the JJs with opposite structural chirality but not for the JJs with the same structural chirality or for single crystals of the same material.