Nonlinear optical and electrical effects associated with a lack of spatial inversion symmetry allow the direction-selective propagation and transport of quantum particles, such as photons and electrons. The most common example of such nonreciprocal phenomena is a semiconductor diode with a p-n junction that has a low resistance in one direction and a high resistance in the other. Although the diode effect today forms the basis of numerous electronic components, such as rectifiers, AC-DC converters, and photodetectors, there inevitably exists an energy loss due to the finite resistance. Therefore, a worthwhile goal is to realize a superconducting diode that has zero resistance only in one direction. I will show the observation of a superconducting diode effect in an artificial superlattice [Nb/V/Ta]n without a center of inversion. This superconducting diode effect would enable the phase coherent and direction selective charge transport [1,2].

[1] F. Ando et al., Nature 584, 373-376 (2020).

[2] T. Ideue and Y. Iwasa, Nature 584, 349-350 (2020).