Giant superconducting diode effect in ion-beam patterned Sn-based superconductor nanowire / topological Dirac semimetal planar heterostructures

Abstract

Superconductor/topological material heterostructures are intensively studied as a platform for topological superconductivity and Majorana physics. However, the high cost of nanofabrication and the difficulty of preparing high-quality interfaces between the two dissimilar materials are common obstacles that hinder the observation of intrinsic physics and the realisation of scalable topological devices and circuits. Here, we demonstrate an innovative method to directly draw nanoscale superconducting beta-tin (beta-Sn) patterns of any shape in the plane of a topological Dirac semimetal (TDS) alpha-tin (alpha-Sn) thin film by irradiating a focused ion beam (FIB). We utilise the property that alpha-Sn undergoes a phase transition to superconducting beta-Sn upon heating by FIB. In beta-Sn nanowires embedded in a TDS alpha-Sn thin film, we observe giant non-reciprocal superconducting transport, where the critical current changes by 69% upon reversing the current direction. The superconducting diode rectification ratio reaches a maximum when the magnetic field is applied parallel to the current, distinguishing itself from all the previous reports. Moreover, it oscillates between alternate signs with increasing magnetic field strength. The angular dependence of the rectification ratio on the magnetic field and current directions is similar to that of the chiral anomaly effect in TDS alpha-Sn, suggesting that the non-reciprocal superconducting transport may occur at the beta-Sn/alpha-Sn interfaces. The ion-beam patterned Sn-based superconductor/TDS planar structures thus show promise as a universal platform for investigating novel quantum physics and devices based on topological superconducting circuits of any shape.