Ultra-Sensitive Microwave, THz, and IR Sensors Based on Tunable Josephson Junctions, Realized in Graphene Moiré Superconductors

OBJECTIVE: Develop highly sensitive tunable sensors in microwave, THz, and IR regions via Josephson Junctions, based on twisted 2D heterostructures of graphene Moir superconductors. DESCRIPTION: In order to address the future demands on sensitivity, robustness and overall multi-functionality, future multi-domain sensing systems in all environments will need highly sensitive sensors with tunable spectral characteristics. A recently emerged novel Moir quantum matter paradigm using two graphene sheets twisted by an angle close to a theoretically predicted magic angle', can result in flat band structure near the Dirac point, giving rise to a strongly-correlated electronic system and enabling quantum phases, such as correlated insulators, Chern insulators, superconductivity, etc. Further advances in modeling, design, fabrication and measurement of twisted 2D heterostructures are needed for better understanding these phenomena in order to be employed for microwave, THz, and far-IR detectors with improved sensitivity by up to three orders of magnitude over current capabilities [a,b]. The goal of this technology development is to design, develop and demonstrate a prototype Moir based tunable detector with improved sensitivity by at least an order of magnitude. While the overall goal is to address the need for advanced detection systems (e.g., microwave, THz, or IR) by exploring new phenomena in Moir quantum materials, here the focus is on the approach of tunable Josephson junction based on graphene Moir superconductors. PHASE I: Develop necessary computational methods, rigorously model the proposed heterostructure-based sensor system, and formulate and provide a detailed plan for fabricating and demonstrating the twistronics-based sensor system. Summarize the recent scientific and technical progress being relied on, relevant to the measurement, modeling, design, and fabrication of twisted 2D heterostructure-based devices. Detail the designs improving microwave, THz, and far-IR detector technology via the Moir superconductivity, and develop and present modeling and quantitative arguments to establish feasibility. PHASE II: Construct and demonstrate prototype devices based on Phase 1 feasibility and design. Apply RF techniques to develop Josephson sensors based on Moir superconductivity [c]. Exploit and demonstrate the gate-tunable superconductivity in the twisted Moir system as a unique opportunity to develop a sensitive detector for lower-energy photons, and for broader bandwidth, that makes it feasible for hyperspectral imaging. Employ higher ratios of kinetic inductance (higher than conventional superconductivity) and demonstrate high signal-to-noise ratios. The twisted Moir system consisting of only two [d] or three [e] active material layers has an extremely small heat capacity, on the order of one Boltzmann constant, which can enable a giant thermal response from even just a single photon. Address practical issues of making consistent twist angles between layers in a reproducible way using a scalable process and incorporate into an atomically thin twisted moir system that has promise of providing the ultimate material platform for microwave and THz sensing. PHASE III DUAL USE APPLICATIONS: The proposer is required to obtain funding from either the private sector, a non-STTR Government source, or both, to develop the prototype into a viable product or non-R&D service for sale in military or private sector markets. STTR Phase III refers to work that derives from, extends, or completes an effort made under prior STTR funding agreements, but is funded by sources other than the STTR Program. Phase III work is typically oriented towards commercialization of STTR research or technology. REFERENCES: a. Observation of the Dirac fluid and the breakdown of the Wiedemann-Franz law in graphene, Crossno, Shi, Wang, Liu, Harzheim, Lucas, Sachdev, P. Kim, Taniguchi, Watanabe, Ohki, Fong, Science 351, 1058 (2016). b. Microwave characterization of Josephson junction arrays: Implementing a low loss superinductance, Masluk, Kamal, Minev, Devoret, Phys. Rev. Lett. 109, 137002 (2012). c. Magic-angle bilayer graphene nanocalorimeters: toward broadband, energy-resolving single photon detection, Seifert, X. Lu, Stepanov, Dur n Retamal, Nano Lett. 20, 3459 (2020). d. Tunable spin-polarized correlated states in twisted double bilayer graphene, Liu, T Taniguchi, A Vishwanath, P Kim, Nature 583, 221-225 (2020). e. Correlated Superconducting and Insulating States in Twisted Trilayer Graphene Moir of Moir Superlattices, Tsai, Luskin, Kaxiras, Wang, et al, arXiv:1912.03375. f. Graphene-based Josephson junction microwave bolometer, Lee, Taniguchi, Watanabe, Kim, Englund, Fong, Nature 586, 20 (2020). g. Josephson-junction infrared single-photon detector, Walsh, Jung, Lee, Efetov, Wu, Kim, Fong, arXiv:2011.02624. KEYWORDS: 2-D heterostructure; Graphene; Moir quantum matter; Twistronics; single photon detection; Superconductivity