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arXiv:1904.08349 · Nano Letters

Field-Effect Controllable Metallic Josephson Interferometer

Federico Paolucci, Francesco Vischi, Giorgio De Simoni, Claudio Guarcello, Paolo Solinas, Francesco Giazotto

Published Aug 28, 2019• 60 citations
arXivHTMLPDF

Abstract

Gate-tunable Josephson junctions (JJs) are the backbone of superconducting classical and quantum computation. Typically, these systems exploit low-charge-concentration materials and present technological difficulties limiting their scalability. Surprisingly, electric field modulation of a supercurrent in metallic wires and JJs has been recently demonstrated. Here, we report the realization of titanium-based monolithic interferometers which allow tuning both JJs independently via voltage bias applied to capacitively coupled electrodes. Our experiments demonstrate full control of the amplitude of the switching current ( I s ) and of the superconducting phase across the single JJ in a wide range of temperatures. Astoundingly, by gate-biasing a single junction, the maximum achievable total I s is suppressed down to values much lower than the critical current of a single JJ. A theoretical model including gate-induced phase fluctuations on a single junction accounts for our experimental findings. This class of quantum interferometers could represent a breakthrough for several applications such as digital electronics, quantum computing, sensitive magnetometry, and single-photon detection.

DOI
10.1021/acs.nanolett.9b02369

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Gate-tunable Josephson junctions (JJs) are the backbone of superconducting classical and quantum computation. Typically, these systems exploit low-charge-concentration materials and present technological difficulties limiting their scalability. Surprisingly, electric field modulation of a supercurrent in metallic wires and JJs has been recently demonstrated. Here, we report the realization of titanium-based monolithic interferometers which allow tuning both JJs independently via voltage bias applied to capacitively coupled electrodes. Our experiments demonstrate full control of the amplitude of the switching current ( I s ) and of the superconducting phase across the single JJ in a wide range of temperatures. Astoundingly, by gate-biasing a single junction, the maximum achievable total I s is suppressed down to values much lower than the critical current of a single JJ. A theoretical model including gate-induced phase fluctuations on a single junction accounts for our experimental findings. This class of quantum interferometers could represent a breakthrough for several applications such as digital electronics, quantum computing, sensitive magnetometry, and single-photon detection.
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Abstract The tunability in Josephson junctions is foundational to the superconducting classical and quantum applications. Here, we demonstrate the local manipulation of supercurrent realized in a superconducting quantum interference device (SQUID) with two Nb/TiO x /Nb Josephson junctions that is biased at the TiO x layer. Our measurements indicate that the multi-port device allows for an easy and in situ tunability of the supercurrent. The control mechanism can be finely explained by simple yet valid theoretical methods, which take an effective electronic temperature across the SQUID and the self inductive magnetic flux into account. Furthermore, we show that the phase difference and kinetic inductance of this device can be tuned locally via the injection current. Thus, the device provides perspective for several superconducting electronics such as tunable superconducting circuits, sensitive magnetometry, and fast digital elements.
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Recently, the possibility to tune the critical current of conventional metallic superconductors via electrostatic gating was shown in wires, Josephson weak-links, and superconductor-normal metal–superconductor junctions. Here, we exploit such a technique to demonstrate a gate-controlled vanadium-based Dayem nano-bridge operated as a half-wave rectifier at 3 K. Our devices exploit the gate-driven modulation of the critical current of the Josephson junction and the resulting steep variation of its normal-state resistance, to convert an AC signal applied to the gate electrode into a DC one across the junction. All-metallic superconducting gated rectifiers could provide the enabling technology to realize tunable photon detectors and diodes useful for superconducting electronics circuitry.
Voltage-Tunable Vertical Nb/TiOx\text{TiO}_{\text{x}}TiOx​/Nb Josephson Junction With High Transconductance and Broad Inductance Modulation
The ability to electrically control the critical current of a Josephson junction is a pivotal capability for developing reconfigurable superconducting electronics and quantum circuits. In this study, we report a voltage-tunable vertical Nb/TiOx\rm{TiO}_{\rm{x}}TiOx​/Nb Josephson junction, featuring a top tuning electrode isolated by a 13 nm single-crystal hexagonal boron nitride (h-BN) dielectric. Applying a tuning voltage across this 2D insulator creates a high electric field, enabling the direct injection of high-energy quasi-particles into the junction. This mechanism facilitates the continuous suppression of the critical current to zero, accompanied by a broad modulation of the Josephson inductance. Our superconducting device exhibits a high transconductance ($\sim1mA/V)andallowstheJosephsonkineticinductancetobetunedacrossawiderange(1 mA/V) and allows the Josephson kinetic inductance to be tuned across a wide range (1mA/V)andallowstheJosephsonkineticinductancetobetunedacrossawiderange(\sim$0.01-1 nH). This voltage-tunable vertical architecture provides a compact device footprint, offering a promising platform for exploring dense, all-metallic superconducting circuits and future active cryogenic applications.