Two-dimensional superconducting diode effect in topological insulator/superconductor heterostructure

The superconducting diode effect (SDE) is a phenomenon where the superconducting critical current depends on the current direction. SDE has garnered significant attention not only from fundamental physics but also from the applications in superconducting electronics. In three-dimensional superconductors, SDE is distinctly observable owing to the sharp jump in the current-voltage (I-V) characteristics. On the other hand, in two-dimensional superconductors, observation of SDE remains an intriguing challenge because the critical current is theoretically zero [1]. Here, we demonstrate the SDE in two-dimensional superconductor realized in a heterostructure consisting of topological insulator Bi₂Te₃ and superconductor FeSe_0.1Te_0.9 grown by molecular beam epitaxy. The observed I-V characteristics reveal nonreciprocity in the vortex-creep regime, where finite voltages arise due to the two-dimensional nature of superconductivity. Furthermore, our 2D film demonstrates abrupt voltage jumps, influenced by both the current flow direction and the transverse magnetic field direction [2]. In the presentation, we will discuss the underlying mechanism of the voltage jump in terms of vortex-flow instability.