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▲ [16p-D704-14] Giant superconducting diode effect in β-Sn nanowires embedded in topological Dirac semimetal α-Sn thin films
Keywords:Topological Dirac semimetal, Superconducting diode effect, topological superconductivity
α-Sn with diamond crystal structure is a promising topological material platform because it can exhibit a wide range of topological phases, from topological Dirac semimetal to topological insulator [1]. Furthermore, α-Sn is known to undergo a phase transition to the bcc-type β-Sn upon heating. As β-Sn becomes superconducting at low temperature (< 4 K), this opens a new way to incorporate superconductivity into the already-rich topological phase diagram of α-Sn. This is expected to realize unconventional superconductivity in the Sn-based material structures.
In this study, we fabricate and investigate the transport properties of superconducting β-Sn nanowires embedded in topological Dirac semimetal α-Sn thin films. Epitaxial α-Sn thin films (thickness of 60 nm) are grown on InSb (001) substrates using molecular beam epitaxy (MBE). The α-Sn films are selectively transformed to β-Sn by irradiating a focused Ga ion-beam. We successfully fabricate β-Sn nanowires with different width W, which can be as small as 180 nm (Fig.1a). The β-Sn nanowires of various W exhibit superconductivity below 4 K. As shown in Fig.1b, upon applying a magnetic field H parallel to the nanowire, the critical current of a β-Sn nanowire with W = 500 nm remarkably changes when reversing the current I. This superconducting diode effect is absent without applying the magnetic field. The superconducting rectification ratio reaches a maximum of 35% at H = 1100 Oe, which is one of the largest ratios reported thus far. We consider a proximity effect between the superconducting β-Sn and the topological Dirac semimetal α-Sn plays an important role in this giant superconducting diode effect.
In this study, we fabricate and investigate the transport properties of superconducting β-Sn nanowires embedded in topological Dirac semimetal α-Sn thin films. Epitaxial α-Sn thin films (thickness of 60 nm) are grown on InSb (001) substrates using molecular beam epitaxy (MBE). The α-Sn films are selectively transformed to β-Sn by irradiating a focused Ga ion-beam. We successfully fabricate β-Sn nanowires with different width W, which can be as small as 180 nm (Fig.1a). The β-Sn nanowires of various W exhibit superconductivity below 4 K. As shown in Fig.1b, upon applying a magnetic field H parallel to the nanowire, the critical current of a β-Sn nanowire with W = 500 nm remarkably changes when reversing the current I. This superconducting diode effect is absent without applying the magnetic field. The superconducting rectification ratio reaches a maximum of 35% at H = 1100 Oe, which is one of the largest ratios reported thus far. We consider a proximity effect between the superconducting β-Sn and the topological Dirac semimetal α-Sn plays an important role in this giant superconducting diode effect.