Superconducting diode effect in InSb nanowires with Tin shell

We study Josephson Junction in InSb nanowires with 15nm Tin shells. We observe critical current diffraction patterns skewed and inversion-symmetric in magnetic field and bias direction. The effect is stronger when the external magnetic field is aligned perpendicular to the nanowire, in the substrate plane. i.e. in the most likely direction of the effective spin-orbit field in the junction. The effect is also tunable by gate voltage. We discuss this effect in the context of phi0-Josephson junction physics, one consequence of which is known in recent literature as superconducting diode effect. We consider alternative explanations such as the effective magnetic field and perform numerical simulations to understand our findings.