講演情報
[22p-A201-4]New superconducting phenomena in Sn-based quantum structures
〇Le Duc Anh1,2,3, Keita Ishihara1, Tomoki Hotta1, Daiki Nishigaki1, Masaaki Tanaka1,3 (1.EEIS, Tokyo Univ., 2.PRESTO, JST, 3.CSRN, Tokyo Univ.)
キーワード：
superconducting diode effect、topological Dirac semimetal、topological superconductivity
In this work, we present a new topological material platform based on Sn, which is one of the earliest and most common metal elements exploited in the human history. Body-center tetragonal β-Sn is a well-known metal that exhibits conventional BCS-type superconductivity below 4 K. On the other hand, diamond-structure α-Sn is a Luttinger semimetal in a bulk condition, which can be transformed to a three-dimensional topological insulator (3D-TI) or a topological Dirac semimetal (TDS) by various means such as strain, thickness, or applying electric field. In their superconducting phase, TDSs such as α-Sn have been theoretically predicted to host Majorana bound states, which are the most desired but not yet established candidate for quantum bits in fault-tolerant quantum computing. Upon heating, α-Sn is known to undergo a phase transition to β-Sn, which thus opens a new way to incorporate superconductivity into the already-rich topological phase diagram of α-Sn. In this work, we demonstrate an innovative method to directly draw any nanoscale superconducting patterns into the plane of a TDS α-Sn thin film using a focused ion beam (FIB), which induces a phase transition of the irradiated α-Sn to a superconducting β-Sn, and new superconducting phenomena such as giant nonreciprocal superconducting transport, where the critical current changes by ±35% upon reversing the current direction.