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arXiv:2507.09478 · Physics Letters A

Perfect superconducting diode and supercurrent range controller

C. P. Sun, Ziqi Zhao, Alexey Bezryadin

Published Oct 10, 2025• 0 citations
arXivHTMLPDF

Abstract

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.

DOI
10.1016/j.physleta.2025.131055

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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.
We suggest using a device called the bootstrap superconducting quantum interference device (BS SQUID) to break the reciprocity in charge transport. This device uses magnetic flux backaction to create a nonreciprocal current-voltage characteristic, which results in a supercurrent rectification coefficient of up to approximately 95%. The BS SQUID works as a quasi-ideal supercurrent diode (SD) and maintains its efficiency up to about 40% of its critical temperature. The external magnetic flux can be used to adjust or reverse the rectification polarity. Finally, we discuss the finite-voltage operation regime of the SD and present a possible application of our device as a half- and full-wave signal rectifier in the microwave regime.
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.
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.
In a SQUID tuned away from half-integer flux (in units of the superconducting flux quantum), the concurrence of multiple Josephson harmonics and an asymmetry between the junctions leads to the Josephson diode effect -- a nonreciprocal current-voltage characteristic manifested as an asymmetry of critical currents at opposite polarities. We predict a dual version of this effect in a gate-tunable Cooper pair transistor placed in series with a highly resistive environment. When tuned away from half-integer gate charge (in units of the Cooper pair charge) it shows an asymmetry of critical voltages at opposite polarities -- a dual diode effect we refer to as the Bloch diode effect. It arises from an asymmetry in the dispersion of the transistor's Bloch bands. A highly resistive environment can be realized with a Josephson junction array, suggesting that such a diode could be implemented using conventional superconducting quantum circuits.
It was recently experimentally proved that the superconducting counterpart of a diode, i.e., a device that realizes nonreciprocal Cooper pairs transport, can be realized by breaking the spatial and time-reversal symmetry of a system simultaneously. Here, we report the theory, fabrication, and operation of a monolithic dc superconducting quantum interference device that embedding three-dimensional Dayem nanobridges as weak links realizes an efficient and magnetic flux-tunable supercurrent diode. The device is entirely realized in Al and achieves a maximum rectification efficiency of ∼20%, which stems from the high harmonic content of its current-to-phase relation only without the need of any sizable screening current caused by a finite loop inductance. Our interferometer can be easily integrated with state-of-the-art superconducting electronics and since it does not require a finite loop inductance to provide large rectification, its downsizing is not limited by the geometrical constraints of the superconducting ring.
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.