Presentation Information
[10a-N303-11]Large field-free superconducting diode effect in α-Sn / β-Sn planar heterostructures
〇Yuta Okuyama1, Le Duc Anh1,2, Masaaki Tanaka1,2 (1.Univ. of Tokyo, 2.CSRN, Univ. of Tokyo)
Keywords:
superconducting diode effect
Fault-tolerant quantum computing (FTQC) is essential for the development of practical quantum computers. Utilizing Majorana zero modes (MZMs) is a promising way to achieve FTQC, and MZMs are theoretically predicted to appear in heterostructures of topological materials and superconductors. Here, we focus on Sn-based planar heterostructures. Sn has α and β phases distinguished by its crystal structure. α-Sn is known as a topological Dirac semimetal (TDS), while β-Sn is a BCS superconductor at low temperature. Recently, we have successfully fabricated β-Sn nanowires embedded in α-Sn by irradiating a focused ion beam (FIB) on α-Sn films and these nanowires exhibit a large superconducting diode effect (SDE) under a non-zero external magnetic field parallel to the current.
In this study, we study the formation and superconducting transport properties of β-Sn nanowires embedded in higher α-Sn thin films under various FIB irradiation conditions. The α-Sn films were grown on InSb (001) substrate by molecular beam epitaxy in an Sb-free chamber at very low temperature (< –20℃) after the growth of an InSb buffer layer. β-Sn nanowires fabricated under the same FIB conditions as in our previous work partially reverted to α-Sn during the cooling process for measuring superconducting properties, exhibiting the "tin pest" phenomenon, and did not show superconducting transition. This suggests that β-Sn regions in these nanowires possess less impurities because impurities such as Sb atoms in β-Sn incorporated from the chamber atmosphere or diffused from the InSb substrate are considered to prevent Sn pest. β-Sn nanowires with larger FIB writing iterations showed superconducting transitions. Upon switching the current direction, a larger critical current difference was observed. Furthermore, a sizable SDE is observed even in the absence of an external magnetic field. This prominent, field-free SDE may be caused by origins different from those of the samples in our previous work.
In this study, we study the formation and superconducting transport properties of β-Sn nanowires embedded in higher α-Sn thin films under various FIB irradiation conditions. The α-Sn films were grown on InSb (001) substrate by molecular beam epitaxy in an Sb-free chamber at very low temperature (< –20℃) after the growth of an InSb buffer layer. β-Sn nanowires fabricated under the same FIB conditions as in our previous work partially reverted to α-Sn during the cooling process for measuring superconducting properties, exhibiting the "tin pest" phenomenon, and did not show superconducting transition. This suggests that β-Sn regions in these nanowires possess less impurities because impurities such as Sb atoms in β-Sn incorporated from the chamber atmosphere or diffused from the InSb substrate are considered to prevent Sn pest. β-Sn nanowires with larger FIB writing iterations showed superconducting transitions. Upon switching the current direction, a larger critical current difference was observed. Furthermore, a sizable SDE is observed even in the absence of an external magnetic field. This prominent, field-free SDE may be caused by origins different from those of the samples in our previous work.