Diode is one of the basic electronic components. It has a nonreciprocal current response, associated with a broken space/time reversal symmetry. Here we demonstrate prototypes of superconducting diodes operational at zero magnetic field. They are based on conventional niobium planar Josephson junctions, in which space/time symmetry is broken by a combination of self-field effect from nonuniform bias and stray fields from a trapped Abrikosov vortex. We demonstrate that nonreciprocity of critical current in such diodes can reach an order of magnitude and rectification efficiency can exceed 70%. Furthermore, we can easily change the diode polarity and switch nonreciprocity on/off by changing the bias configuration and by trapping/removing of a vortex. This facilitates a memory functionality. We argue that such a diode-with-memory can be used for a future generation of in-memory superconducting computers.
Diode is one of the basic electronic components. It has a nonreciprocal current response, associated with a broken space/time reversal symmetry. Here we demonstrate prototypes of superconducting diodes operational at zero magnetic field. They are based on conventional niobium planar Josephson junctions, in which space/time symmetry is broken by a combination of self-field effect from nonuniform bias and stray fields from a trapped Abrikosov vortex. We demonstrate that nonreciprocity of critical current in such diodes can reach an order of magnitude and rectification efficiency can exceed 70%. Furthermore, we can easily change the diode polarity and switch nonreciprocity on/off by changing the bias configuration and by trapping/removing of a vortex. This facilitates a memory functionality. We argue that such a diode-with-memory can be used for a future generation of in-memory superconducting computers.
Efficient, scalable, and magnetic-field-free superconducting diodes are essential for future superconducting electronics; yet, despite significant efforts, such practical devices remain unrealized. The main challenge lies in achieving broad-range in-situ tunability, both for optimization and for achieving transistor-like operation. Here, we study diodes based on four-terminal niobium planar Josephson junctions. We show that the multiterminal structure eliminates the need for an external magnetic field and enables essentially unrestricted in-situ tunability, along with reconfigurability of the diode polarity, leading to new functionality. For example, we demonstrate that such diodes can operate as Gauss neurons via reentrant superconductivity. By deliberately tuning the junction parameters, we obtain effectively infinite nonreciprocity (within experimental resolution) leading to threshold-free ac-current rectification. Such technologically simple, reconfigurable, and broadly tunable diodes could be instrumental for future digital and neuromorphic computing.
Superconducting electronics offer significant advantages in speed and power efficiency for next-generation computing and communication systems. However, their practical deployment is limited by the absence of simple, efficient, and scalable superconducting counterparts to key semiconductor components. In this work, we investigate diodes based on planar Josephson junctions fabricated from a conventional niobium superconductor. The nonreciprocity in these diodes arises from the self-field effect induced by the geometrical asymmetry of the junction. By deliberate tuning of the junction parameters, we achieved effectively infinite nonreciprocity (within experimental resolution), characterized by a complete suppression of the superconducting critical current in one direction while maintaining a significant current in the opposite direction. The key novelty of this work lies in the demonstration of the optical diode effect. We observed threshold-free rectification of 75 GHz microwave radiation, indicating that these diodes exhibit near-ideal optical nonreciprocity. Our results open new avenues for ultrafast superconducting electronics and lay the groundwork for wireless sub-THz signal processing.
We demonstrate a practical, field-free superconducting diode based on conventional Nb thin-film technology by integrating an intrinsic superconducting phase battery with an asymmetric DC superconducting quantum interference device. Unlike other approaches that require external magnetic fields or gate voltages to break time-reversal symmetry, our design achieves nonreciprocal supercurrents with on-chip phase bias, making it highly suitable for practical applications. The critical operational parameters, including the backward breakdown voltage and reverse resistance, are well defined by the Nb film gap voltage (∼2.8 mV) and the sub-gap resistance of the un-shunted Nb/Al–AlOx/Nb Josephson junctions. The resulting diode exhibits a forward supercurrent of 168 μA at 4.2 K, with a diode efficiency reaching 40%, a comprehensive performance exceeding prior field-free superconducting diodes. To validate its practicality, we fabricate and characterize a superconducting full-wave rectifier consisting of four such diodes. The demonstration of this rectifier highlights its potential as a DC source for superconducting digital circuits, paving the way for scalable, energy-efficient superconducting electronics.
Ultrathin superconducting (SC) films embedded between two ferromagnetic insulators (FI) experience magnetic-exchange coupling, enabling the switching of the superconducting state by controlling the relative FI magnetization alignment. We investigate micrometer-scale devices patterned from such thin-film heterostructures and demonstrate their reproducible operation as nonreciprocal superconducting memory elements. Single-cell writing is realized using current-pulse-induced, heat-assisted magnetic switching. Furthermore, at a lower temperature, symmetry breaking gives the memory elements a marked nonreciprocity, with zero magnetic field superconducting diode efficiencies exceeding ±60%. These results present highly scalable FI/SC/FI hybrid structures as a contender for state-of-the art robust superconducting memories for neuromorphic superconducting computing and new data guiding schemes.
Abstract Back-action refers to a response that retro-acts on a system to tailor its properties with respect to an external stimulus. This self-induced effect generally belongs to both the natural and technological realm, ranging from neural networks [1] to optics [2] and electronic circuitry [3]. In electronics, back-action mechanisms are at the heart of many classes of devices such as amplifiers, oscillators, and sensors [4]. Here, we demonstrate that back-action can be successfully exploited to achieve non-reciprocal transport in superconducting circuits. Our device realizes a supercurrent diode, since the dissipationless current flows in one direction whereas dissipative transport occurs in the opposite direction. Supercurrent diodes presented so far rely on magnetic elements or vortices to mediate charge transport or external magnetic fields to break time-reversal symmetry [5-9]. In our implementation, back-action solely turns a conventional reciprocal superconducting weak link with no asymmetry between the current bias directions into a diode, where the critical current amplitude depends on the bias sign. The self-interaction of the supercurrent with the device stems from the gate tunability of the critical current, which uniquely promotes up to 88% of magnetic field-free signal rectification and diode functionality with selectable polarity. The concept we introduce is very general and can be applied directly to a large variety of devices, thereby opening novel functionalities in superconducting electronics.
Diodes have a nonreciprocal voltage versus current relationship, produced by breaking the space and time reversal symmetry. However, developing high-end superconducting computers requires a superconducting analogue of the traditional semiconductor diode. Such a superconducting diode exhibits non-reciprocity, or a high asymmetry in its critical currents. We present a model of a perfect superconducting diode based on a superconducting quantum interference device made with multiple superconducting nanowires. The diode predicted by our model has a large positive critical current, while the negative critical current can be exactly zero. This 100% diode efficiency ( η = 1 ) remains stable against small changes of the magnetic field. Another important result is that under certain and quite broad conditions such devices can act as supercurrent range controllers. In such device a supercurrent can flow with zero voltage applied, but only if the supercurrent is contained in some narrow, adjustable range, which excludes zero current.