Nonreciprocal transport refers to charge transfer processes that are sensitive to the bias polarity. Until recently, nonreciprocal transport was studied only in dissipative systems, where the nonreciprocal quantity is the resistance. Recent experiments have, however, demonstrated nonreciprocal supercurrent leading to the observation of a supercurrent diode effect in Rashba superconductors. Here we report on a supercurrent diode effect in NbSe₂ constrictions obtained by patterning NbSe₂ flakes with both even and odd layer number. The observed rectification is a consequence of the valley-Zeeman spin-orbit interaction. We demonstrate a rectification efficiency as large as 60%, considerably larger than the efficiency of devices based on Rashba superconductors. In agreement with recent theory for superconducting transition metal dichalcogenides, we show that the effect is driven by the out-of-plane component of the magnetic field. Remarkably, we find that the effect becomes field-asymmetric in the presence of an additional in-plane field component transverse to the current direction. Supercurrent diodes offer a further degree of freedom in designing superconducting quantum electronics with the high degree of integrability offered by van der Waals materials.

不可逆传输是指对偏压极性敏感的电荷传输过程。直到最近，不可逆输运仅在耗散系统中进行研究，其中不可逆量是阻力。然而，最近的实验证明了不可逆超电流导致在拉什巴超导体中观察到超电流二极管效应。在这里，我们报告了通过对具有偶数和奇数层数的 NbSe ₂薄片进行图案化而获得的 NbSe ₂收缩中的超电流二极管效应。观察到的整流是谷-塞曼自旋轨道相互作用的结果。我们展示了高达 60% 的整流效率，远远高于基于 Rashba 超导体的设备的效率。与超导过渡金属二硫属化物的最新理论一致，我们表明该效应是由磁场的面外分量驱动的。值得注意的是，我们发现，在存在横向于电流方向的附加面内场分量的情况下，该效应变得场不对称。超流二极管通过范德华材料提供的高度可集成性，为超导量子电子器件的设计提供了更大的自由度。