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Golod T, Morlet-Decarnin L, Krasnov VM. Word and bit line operation of a 1 × 1 μm 2 superconducting vortex-based memory. Nat Commun 2023; 14:4926. [PMID: 37582835 PMCID: PMC10427686 DOI: 10.1038/s41467-023-40654-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2023] [Accepted: 08/01/2023] [Indexed: 08/17/2023] Open
Abstract
The lack of dense random access memory is one of the main bottlenecks for the creation of a digital superconducting computer. In this work we study experimentally vortex-based superconducting memory cells. Three main results are obtained. First, we test scalability and demonstrate that the cells can be straightforwardly miniaturized to submicron sizes. Second, we emphasize the importance of conscious geometrical engineering. In the studied devices we introduce an asymmetric easy track for vortex motion and show that it enables a controllable manipulation of vortex states. Finally, we perform a detailed analysis of word and bit line operation of a 1 × 1 μm2 cell. High-endurance, non-volatile operation at zero magnetic field is reported. Remarkably, we observe that the combined word and bit line threshold current is significantly reduced compared to the bare word-line operation. This could greatly improve the selectivity of individual cell addressing in a multi-cell RAM. The achieved one square micron area is an important milestone and a significant step forward towards creation of a dense cryogenic memory.
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Affiliation(s)
- Taras Golod
- Department of Physics, Stockholm University, AlbaNova University Center, SE-10691, Stockholm, Sweden
| | - Lise Morlet-Decarnin
- Department of Physics, Stockholm University, AlbaNova University Center, SE-10691, Stockholm, Sweden
| | - Vladimir M Krasnov
- Department of Physics, Stockholm University, AlbaNova University Center, SE-10691, Stockholm, Sweden.
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2
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Krasnov VM. A distributed active patch antenna model of a Josephson oscillator. BEILSTEIN JOURNAL OF NANOTECHNOLOGY 2023; 14:151-164. [PMID: 36761677 PMCID: PMC9887756 DOI: 10.3762/bjnano.14.16] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/11/2022] [Accepted: 01/13/2023] [Indexed: 06/18/2023]
Abstract
Optimization of Josephson oscillators requires a quantitative understanding of their microwave properties. A Josephson junction has a geometry similar to a microstrip patch antenna. However, it is biased by a dc current distributed over the whole area of the junction. The oscillating electric field is generated internally via the ac-Josephson effect. In this work, I present a distributed, active patch antenna model of a Josephson oscillator. It takes into account the internal Josephson electrodynamics and allows for the determination of the effective input resistance, which couples the Josephson current to cavity modes in the transmission line formed by the junction. The model provides full characterization of Josephson oscillators and explains the origin of the low radiative power efficiency. Finally, I discuss the design of an optimized Josephson patch oscillator capable of reaching high efficiency and radiation power for emission into free space.
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Affiliation(s)
- Vladimir M Krasnov
- Department of Physics, Stockholm University, AlbaNova University Center, SE-10691 Stockholm, Sweden
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Cattaneo R, Galin MA, Krasnov VM. Observation of collective excitation of surface plasmon resonances in large Josephson junction arrays. BEILSTEIN JOURNAL OF NANOTECHNOLOGY 2022; 13:1578-1588. [PMID: 36636736 PMCID: PMC9811307 DOI: 10.3762/bjnano.13.132] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/18/2022] [Accepted: 11/29/2022] [Indexed: 06/17/2023]
Abstract
Josephson junctions can be used as sources of microwave radiation. However, synchronization of many junctions is required for achieving a coherent amplification of the emitted power. In this work we present an experimental study of large arrays containing up to one thousand Nb/Nb x Si1- x /Nb junctions. The arrays exhibit profound cavity mode resonances, corresponding to the formation of standing waves at the electrode/substrate interface. We observe that resonant steps in the current-voltage characteristics appear above some threshold number of junctions, N th ≈ 100, and then progressively enhance in amplitude with further increment of the number of junctions in the resistive oscillating state. We use an external detector to measure the emission of electromagnetic waves. The emission power correlates with the step amplitude. Our results indicate that the emission is facilitated by the cavity modes in the electrodes. The modes are collectively excited by active junctions. In turn, the standing wave imprints its order on the array, facilitating mutual phase-locking of junctions. This provides an indirect coupling mechanism, allowing for the synchronization of junctions, which do not directly interact with each other. Our results demonstrate that electrodes can effectively work as a common external resonator, facilitating long-range phase-locking of large junction arrays with sizes larger than the emitted wavelength.
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Affiliation(s)
- Roger Cattaneo
- Stockholm University, Physics Department, SE-10691 Stockholm, Sweden
| | - Mikhail A Galin
- Institute for Physics of Microstructures RAS, 603950 Nizhny Novgorod, Russia
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Galin MA, Krasnov VM, Shereshevsky IA, Vdovicheva NK, Kurin VV. Coherent amplification of radiation from two phase-locked Josephson junction arrays. BEILSTEIN JOURNAL OF NANOTECHNOLOGY 2022; 13:1445-1457. [PMID: 36570615 PMCID: PMC9749501 DOI: 10.3762/bjnano.13.119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/01/2022] [Accepted: 11/01/2022] [Indexed: 06/17/2023]
Abstract
We analyze experimentally and theoretically mutual phase locking and electromagnetic interaction between two linear arrays with a large number of Josephson junctions. Arrays with different separation, either on the same chip or on two separate substrates are studied. We observe a large coherent gain, up to a factor of three, of emitted power from two simultaneously biased arrays, compared to the sum of powers from two individually biased arrays. The phenomenon is attributed to the phase locking of junctions in different arrays via a common electromagnetic field. Remarkably, the gain can exceed the factor of two expected for a simple constructive interference of two oscillators. The larger gain is explained by an additional consequence of mutual interaction between two large arrays. Mutual phase locking of large arrays does not only result in constructive interference outside the arrays, but also improved synchronization of junctions inside each array. Our conclusion is supported by numerical modelling.
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Affiliation(s)
- Mikhail A Galin
- Institute for Physics of Microstructures RAS, 603950 Nizhny Novgorod, Russia
| | - Vladimir M Krasnov
- Department of Physics, Stockholm University, AlbaNova University Center, SE-10691 Stockholm, Sweden
| | - Ilya A Shereshevsky
- Institute for Physics of Microstructures RAS, 603950 Nizhny Novgorod, Russia
| | | | - Vladislav V Kurin
- Institute for Physics of Microstructures RAS, 603950 Nizhny Novgorod, Russia
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Coherent emission from surface Josephson plasmons in striped cuprates. Proc Natl Acad Sci U S A 2022; 119:e2211670119. [PMID: 36126100 PMCID: PMC9522412 DOI: 10.1073/pnas.2211670119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
We observe anomalous terahertz emission in photo-excited high-TC cuprates with coexisting superconductivity and charge-stripe order, in absence of any external magnetic field or current bias. Because this phenomenon should be forbidden by symmetry, our observation indicates a symmetry breaking in the stripe phase. The emission spectrum reveals the excitation of surface Josephson plasmons, which are generally dark modes but become coupled to the electromagnetic continuum in these materials by the presence of stripes. The study of coherent anomalous terahertz emission emerges as a sensitive tool to probe the symmetry of superconductors in the presence of frustrated couplings, which is a key topic in the physics of these materials. The interplay between charge order and superconductivity remains one of the central themes of research in quantum materials. In the case of cuprates, the coupling between striped charge fluctuations and local electromagnetic fields is especially important, as it affects transport properties, coherence, and dimensionality of superconducting correlations. Here, we study the emission of coherent terahertz radiation in single-layer cuprates of the La2-xBaxCuO4 family, for which this effect is expected to be forbidden by symmetry. We find that emission vanishes for compounds in which the stripes are quasi-static but is activated when c-axis inversion symmetry is broken by incommensurate or fluctuating charge stripes, such as in La1.905Ba0.095CuO4 and in La1.845Ba0.155CuO4. In this case, terahertz radiation is emitted by surface Josephson plasmons, which are generally dark modes, but couple to free space electromagnetic radiation because of the stripe modulation.
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Golod T, Krasnov VM. Demonstration of a superconducting diode-with-memory, operational at zero magnetic field with switchable nonreciprocity. Nat Commun 2022; 13:3658. [PMID: 35760801 PMCID: PMC9237109 DOI: 10.1038/s41467-022-31256-w] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2022] [Accepted: 06/10/2022] [Indexed: 11/09/2022] Open
Abstract
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.
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Affiliation(s)
- Taras Golod
- Department of Physics, Stockholm University, AlbaNova University Center, SE-10691, Stockholm, Sweden
| | - Vladimir M Krasnov
- Department of Physics, Stockholm University, AlbaNova University Center, SE-10691, Stockholm, Sweden.
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Krasnov MM, Novikova ND, Cattaneo R, Kalenyuk AA, Krasnov VM. Design aspects of Bi 2Sr 2CaCu 2O 8+δ THz sources: optimization of thermal and radiative properties. BEILSTEIN JOURNAL OF NANOTECHNOLOGY 2021; 12:1392-1403. [PMID: 35004123 PMCID: PMC8712971 DOI: 10.3762/bjnano.12.103] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/30/2021] [Accepted: 12/02/2021] [Indexed: 06/14/2023]
Abstract
Impedance matching and heat management are important factors influencing the performance of terahertz sources. In this work we analyze thermal and radiative properties of such devices based on mesa structures of a layered high-temperature superconductor Bi2Sr2CaCu2O8+δ. Two types of devices are considered containing either a conventional large single crystal or a whisker. We perform numerical simulations for various geometrical configurations and parameters and make a comparison with experimental data for the two types of devices. It is demonstrated that the structure and the geometry of both the superconductor and the electrodes play important roles. In crystal-based devices an overlap between the crystal and the electrode leads to appearance of a large parasitic capacitance, which shunts terahertz emission and prevents impedance matching with open space. The overlap is avoided in whisker-based devices. Furthermore, the whisker and the electrodes form a turnstile (crossed-dipole) antenna facilitating good impedance matching. This leads to more than an order of magnitude enhancement of the radiation power efficiency in whisker-based, compared to crystal-based, devices. These results are in good agreement with presented experimental data.
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Affiliation(s)
- Mikhail M Krasnov
- Keldysh Institute of Applied Mathematics of RAS, Moscow, Russia
- Moscow Institute of Physics and Technology, 141700 Dolgoprudny, Russia
| | - Natalia D Novikova
- Keldysh Institute of Applied Mathematics of RAS, Moscow, Russia
- Moscow Institute of Physics and Technology, 141700 Dolgoprudny, Russia
| | - Roger Cattaneo
- Department of Physics, Stockholm University, AlbaNova University Center, SE-10691 Stockholm, Sweden
| | - Alexey A Kalenyuk
- Department of Physics, Stockholm University, AlbaNova University Center, SE-10691 Stockholm, Sweden
- Institute of Metal Physics of National Academy of Sciences of Ukraine, 03142 Kyiv, Ukraine
- Kyiv Academic University, 03142 Kyiv, Ukraine
| | - Vladimir M Krasnov
- Moscow Institute of Physics and Technology, 141700 Dolgoprudny, Russia
- Department of Physics, Stockholm University, AlbaNova University Center, SE-10691 Stockholm, Sweden
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Kalhor S, Ghanaatshoar M, Joyce HJ, Ritchie DA, Kadowaki K, Delfanazari K. Millimeter-Wave-to-Terahertz Superconducting Plasmonic Waveguides for Integrated Nanophotonics at Cryogenic Temperatures. MATERIALS 2021; 14:ma14154291. [PMID: 34361488 PMCID: PMC8347570 DOI: 10.3390/ma14154291] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/08/2021] [Revised: 06/27/2021] [Accepted: 07/07/2021] [Indexed: 12/03/2022]
Abstract
Plasmonics, as a rapidly growing research field, provides new pathways to guide and modulate highly confined light in the microwave-to-optical range of frequencies. We demonstrated a plasmonic slot waveguide, at the nanometer scale, based on the high-transition-temperature (Tc) superconductor Bi2Sr2CaCu2O8+δ (BSCCO), to facilitate the manifestation of chip-scale millimeter wave (mm-wave)-to-terahertz (THz) integrated circuitry operating at cryogenic temperatures. We investigated the effect of geometrical parameters on the modal characteristics of the BSCCO plasmonic slot waveguide between 100 and 800 GHz. In addition, we investigated the thermal sensing of the modal characteristics of the nanoscale superconducting slot waveguide and showed that, at a lower frequency, the fundamental mode of the waveguide had a larger propagation length, a lower effective refractive index, and a strongly localized modal energy. Moreover, we found that our device offered a larger SPP propagation length and higher field confinement than the gold plasmonic waveguides at broad temperature ranges below BSCCO’s Tc. The proposed device can provide a new route toward realizing cryogenic low-loss photonic integrated circuitry at the nanoscale.
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Affiliation(s)
- Samane Kalhor
- Laser and Plasma Research Institute, Shahid Beheshti University, Tehran 19839-69411, Iran; (S.K.); (M.G.)
| | - Majid Ghanaatshoar
- Laser and Plasma Research Institute, Shahid Beheshti University, Tehran 19839-69411, Iran; (S.K.); (M.G.)
| | - Hannah J. Joyce
- Electrical Engineering Division, University of Cambridge, Cambridge CB3 0FA, UK;
| | - David A. Ritchie
- Department of Physics, Cavendish Laboratory, University of Cambridge, Cambridge CB3 0FA, UK;
| | - Kazuo Kadowaki
- Division of Materials Science, Faculty of Pure & Applied Sciences, University of Tsukuba 1-1-1, Tennodai, Tsukuba, Ibaraki 305-8573, Japan;
| | - Kaveh Delfanazari
- Electrical Engineering Division, University of Cambridge, Cambridge CB3 0FA, UK;
- Department of Physics, Cavendish Laboratory, University of Cambridge, Cambridge CB3 0FA, UK;
- James Watt School of Engineering, University of Glasgow, Glasgow G12 8QQ, UK
- Correspondence:
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Kashiwagi T, Yuasa T, Kuwano G, Yamamoto T, Tsujimoto M, Minami H, Kadowaki K. Study of Radiation Characteristics of Intrinsic Josephson Junction Terahertz Emitters with Different Thickness of Bi 2Sr 2CaCu 2O 8+δ Crystals. MATERIALS (BASEL, SWITZERLAND) 2021; 14:1135. [PMID: 33670854 PMCID: PMC7957731 DOI: 10.3390/ma14051135] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/31/2020] [Revised: 02/19/2021] [Accepted: 02/20/2021] [Indexed: 11/16/2022]
Abstract
The radiation intensity from the intrinsic Josephson junction high-Tc superconductor Bi2Sr2CaCu2O8+δ terahertz emitters (Bi2212-THz emitters) is one of the most important characteristics for application uses of the device. In principle, it would be expected to be improved with increasing the number of intrinsic Josephson junctions N in the emitters. In order to further improve the device characteristics, we have developed a stand alone type of mesa structures (SAMs) of Bi2212 crystals. Here, we understood the radiation characteristics of our SAMs more deeply, after we studied the radiation characteristics from three SAMs (S1, S2, and S3) with different thicknesses. Comparing radiation characteristics of the SAMs in which the number of intrinsic Josephson junctions are N∼ 1300 (S1), 2300 (S2), and 3100 (S3), respectively, the radiation intensity, frequency as well as the characteristics of the device working bath temperature are well understood. The strongest radiation of the order of few tens of microwatt was observed from the thickest SAM of S3. We discussed this feature through the N2-relationship and the radiation efficiency of a patch antenna. The thinner SAM of S1 can generate higher radiation frequencies than the thicker one of S3 due to the difference of the applied voltage per junctions limited by the heat-removal performance of the device structures. The observed features in this study are worthwhile designing Bi2212-THz emitters with better emission characteristics for many applications.
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Affiliation(s)
- Takanari Kashiwagi
- Graduate School of Pure & Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8571, Japan; (T.Y.); (G.K.); (M.T.); (H.M.)
- Division of Materials Science, Faculty of Pure & Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8573, Japan
| | - Takumi Yuasa
- Graduate School of Pure & Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8571, Japan; (T.Y.); (G.K.); (M.T.); (H.M.)
| | - Genki Kuwano
- Graduate School of Pure & Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8571, Japan; (T.Y.); (G.K.); (M.T.); (H.M.)
| | - Takashi Yamamoto
- QuTech, Delft University of Technology, PO Box 5046, 2600 GA Delft, The Netherlands;
| | - Manabu Tsujimoto
- Graduate School of Pure & Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8571, Japan; (T.Y.); (G.K.); (M.T.); (H.M.)
- Division of Materials Science, Faculty of Pure & Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8573, Japan
| | - Hidetoshi Minami
- Graduate School of Pure & Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8571, Japan; (T.Y.); (G.K.); (M.T.); (H.M.)
- Division of Materials Science, Faculty of Pure & Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8573, Japan
| | - Kazuo Kadowaki
- Algae Biomass and Energy System R & D Center, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8572, Japan;
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Villegas KHA, Kusmartsev FV, Luo Y, Savenko IG. Optical Transistor for Amplification of Radiation in a Broadband Terahertz Domain. PHYSICAL REVIEW LETTERS 2020; 124:087701. [PMID: 32167339 DOI: 10.1103/physrevlett.124.087701] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/30/2018] [Revised: 10/13/2019] [Accepted: 01/23/2020] [Indexed: 06/10/2023]
Abstract
We propose a new type of optical transistor for a broadband amplification of terahertz radiation. It is made of a graphene-superconductor hybrid, where electrons and Cooper pairs couple by Coulomb forces. The transistor operates via the propagation of surface plasmons in both layers, and the origin of amplification is the quantum capacitance of graphene. It leads to terahertz waves amplification, the negative power absorption, and as a result, the system yields positive gain, and the hybrid acts like an optical transistor, operating with the terahertz light. It can, in principle, amplify even a whole spectrum of chaotic signals (or noise), which is required for numerous biological applications.
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Affiliation(s)
- K H A Villegas
- Center for Theoretical Physics of Complex Systems, Institute for Basic Science (IBS), Daejeon 34126, Korea
| | - F V Kusmartsev
- Micro/Nano Fabrication Laboratory (MNFL), Microsystem and Terahertz Research Center, Chengdu, China
- Physics Department, Loughborough University, Loughborough LE11 3TU, United Kingdom
| | - Y Luo
- Micro/Nano Fabrication Laboratory (MNFL), Microsystem and Terahertz Research Center, Chengdu, China
| | - I G Savenko
- Center for Theoretical Physics of Complex Systems, Institute for Basic Science (IBS), Daejeon 34126, Korea
- A. V. Rzhanov Institute of Semiconductor Physics, Siberian Branch of Russian Academy of Sciences, Novosibirsk 630090, Russia
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