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Krasnov, Vladimir M., Prof. Dr.ORCID iD iconorcid.org/0000-0002-3131-8658
Alternative names
Biography [eng]

February 2005. Professor in Experimental Condensed Matter Physics with focus on mesoscopic phenomena, Department of Physics, Stockholm University, Sweden

January 2004. Docent competence in Applied Physics, Department of Microtechnology and Nanoscience (MINA), Chalmers University of Technology, Göteborg, Sweden.

October 1995. Ph.D. in Physics and Mathematics, Institute of Solid State Physics, Chernogolovka, Russia. Thesis title: "Investigation of magnetic properties and dimensional transitions in layered superconducting structures". 

June 1990, M.Sc. in Engineering Physics, Moscow Institute of Physics and Technology, USSR (diploma cum laude, av >4.75/5.0). Thesis title: "Study of static magnetic properties of HTSC single crystals".

June 1984: Golden medal for graduation from high school (av 5.0/5.0), USSR  

Born 01 June 1967, USSR

Publications (10 of 69) Show all publications
Krasnov, V. M. (2023). A distributed active patch antenna model of a Josephson oscillator. Beilstein Journal of Nanotechnology, 14, 151-164
Open this publication in new window or tab >>A distributed active patch antenna model of a Josephson oscillator
2023 (English)In: Beilstein Journal of Nanotechnology, ISSN 2190-4286, Vol. 14, p. 151-164Article in journal (Refereed) Published
Abstract [en]

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.

Keywords
antenna theory, cavity modes, Josephson effect, terahertz radiation
National Category
Nano Technology Materials Engineering Condensed Matter Physics
Identifiers
urn:nbn:se:su:diva-215287 (URN)10.3762/bjnano.14.16 (DOI)000925846200001 ()36761677 (PubMedID)2-s2.0-85172242198 (Scopus ID)
Available from: 2023-03-23 Created: 2023-03-23 Last updated: 2023-10-06Bibliographically approved
Golod, T., Morlet-Decarnin, L. & Krasnov, V. M. (2023). Word and bit line operation of a 1 x 1 μm2 superconducting vortex-based memory. Nature Communications, 14(1), Article ID 4926.
Open this publication in new window or tab >>Word and bit line operation of a 1 x 1 μm2 superconducting vortex-based memory
2023 (English)In: Nature Communications, E-ISSN 2041-1723, Vol. 14, no 1, article id 4926Article in journal (Refereed) Published
Abstract [en]

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 x 1 mu m(2) 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.

National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:su:diva-223759 (URN)10.1038/s41467-023-40654-7 (DOI)001051523700007 ()37582835 (PubMedID)2-s2.0-85168067364 (Scopus ID)
Available from: 2023-11-15 Created: 2023-11-15 Last updated: 2023-11-15Bibliographically approved
Galin, M. A., Krasnov, V. M., Shereshevsky, I. A., Vdovicheva, N. K. & Kurin, V. V. (2022). Coherent amplification of radiation from two phase-locked Josephson junction arrays. Beilstein Journal of Nanotechnology, 13, 1445-1457
Open this publication in new window or tab >>Coherent amplification of radiation from two phase-locked Josephson junction arrays
Show others...
2022 (English)In: Beilstein Journal of Nanotechnology, ISSN 2190-4286, Vol. 13, p. 1445-1457Article in journal (Refereed) Published
Abstract [en]

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.

Keywords
coherent radiation, Josephson junction arrays, numerical modelling, single-strip line, synchronization
National Category
Physical Chemistry
Identifiers
urn:nbn:se:su:diva-213398 (URN)10.3762/bjnano.13.119 (DOI)000893234800001 ()36570615 (PubMedID)
Available from: 2023-01-05 Created: 2023-01-05 Last updated: 2023-01-05Bibliographically approved
Golod, T. & Krasnov, V. M. (2022). Demonstration of a superconducting diode-with-memory, operational at zero magnetic field with switchable nonreciprocity. Nature Communications, 13(1), Article ID 3658.
Open this publication in new window or tab >>Demonstration of a superconducting diode-with-memory, operational at zero magnetic field with switchable nonreciprocity
2022 (English)In: Nature Communications, E-ISSN 2041-1723, Vol. 13, no 1, article id 3658Article in journal (Refereed) Published
Abstract [en]

Superconducting diodes, operational at zero magnetic field, can be used in supercomputers. Here, the authors demonstrate prototypes of diodes-with-memory, based on Nb Josephson junctions, with a large and switchable nonreciprocity at zero field. 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.

National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:su:diva-207428 (URN)10.1038/s41467-022-31256-w (DOI)000818961600001 ()35760801 (PubMedID)
Available from: 2022-07-27 Created: 2022-07-27 Last updated: 2023-03-28Bibliographically approved
Hovhannisyan, R. A., Golod, T. & Krasnov, V. M. (2022). Holographic reconstruction of magnetic field distribution in a Josephson junction from diffraction-like Ic(H) patterns. Physical Review B, 105(21), Article ID 214513.
Open this publication in new window or tab >>Holographic reconstruction of magnetic field distribution in a Josephson junction from diffraction-like Ic(H) patterns
2022 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 105, no 21, article id 214513Article in journal (Refereed) Published
Abstract [en]

A general problem of magnetic sensors is a trade-off between spatial resolution and magnetic-field sensitivity. With decreasing sensor size its resolution is improved but the sensitivity is deteriorated. Obviation of such a trade-off requires development of super-resolution imaging technique not limited by sensor size. Here we present a proof of concept for a super-resolution method of magnetic imaging by a Josephson junction (JJ). It is based on a solution of an inverse problem—reconstruction of a local magnetic-field distribution within a junction from the dependence of the critical current on an external magnetic field, Ic(H). The method resembles the Fourier-transform holography, with the diffractionlike Ic(H) pattern serving as a hologram. A simple inverse problem solution, valid for an arbitrary symmetric case, is derived. We verify the method numerically and show that the accuracy of reconstruction does not depend on the junction size and is only limited by the field range of the Ic(H) pattern. Finally, the method is tested experimentally using planar Nb JJs. Super-resolution reconstruction of stray magnetic fields from an Abrikosov vortex, trapped in the junction electrodes, is demonstrated. Thus our method facilitates both high field sensitivity and high spatial resolution, obviating the trade-off problem of magnetic sensors. We conclude that the holographic magnetic imaging by a planar JJ can be used in scanning probe microscopy

Keywords
Holography, Josephson effect
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:su:diva-208507 (URN)10.1103/PhysRevB.105.214513 (DOI)000829344500002 ()2-s2.0-85133516801 (Scopus ID)
Available from: 2022-08-30 Created: 2022-08-30 Last updated: 2022-08-30Bibliographically approved
Krasnov, V. M. (2022). How to Write a Contemporary Scientific Article?. Education Research International, 2022, Article ID 5156888.
Open this publication in new window or tab >>How to Write a Contemporary Scientific Article?
2022 (English)In: Education Research International, ISSN 2090-4002, E-ISSN 2090-4010, Vol. 2022, article id 5156888Article in journal (Refereed) Published
Abstract [en]

Today, scientists are drowned in information and have no time to read all publications, even in a specific area. Information is sifted and only a small fraction of articles is read. Under these circumstances, scientific articles have to be properly adjusted to pass through the superficial sifting. Here, I present instructions for PhD students with almost serious advice on how to write (and how not to write) a contemporary scientific article. I argue that it should “tell a story” and should answer on the three main questions: Why, What, and So what?

National Category
Educational Sciences
Identifiers
urn:nbn:se:su:diva-211023 (URN)10.1155/2022/5156888 (DOI)000876301300001 ()
Available from: 2022-11-09 Created: 2022-11-09 Last updated: 2022-11-09Bibliographically approved
Grebenchuk, S. Y., Cattaneo, R. & Krasnov, V. M. (2022). Nonlocal Long-Range Synchronization of Planar Josephson-Junction Arrays. Physical Review Applied, 17(6), Article ID 064032.
Open this publication in new window or tab >>Nonlocal Long-Range Synchronization of Planar Josephson-Junction Arrays
2022 (English)In: Physical Review Applied, E-ISSN 2331-7019, Vol. 17, no 6, article id 064032Article in journal (Refereed) Published
Abstract [en]

We study arrays of planar Nb Josephson junctions with contacts to intermediate electrodes, which allow measurements of individual junctions and, thus, provide an insight into intricate array dynamics. We observe strong indications for array phase locking, despite a significant interjunction separation. Several unusual phenomena are reported, such as a bistable critical current with reentrant superconductivity upon switching of nearby junctions; and “incorrect” Shapiro steps, occurring at mixing frequencies between the external rf radiation and the internal Josephson frequency in nearby junctions. Our results reveal a surprisingly strong and long-range interjunction interaction, which is attributed to nonlocality of planar-junction electrodynamics, caused by the long-range spreading of stray electromagnetic fields. The nonlocality greatly enhances the high-frequency interjunction coupling and enables large-scale synchronization. Therefore, we conclude that planar geometry is advantageous for the realization of coherent Josephson electronics.

National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:su:diva-207438 (URN)10.1103/PhysRevApplied.17.064032 (DOI)000817873900001 ()
Available from: 2022-07-26 Created: 2022-07-26 Last updated: 2022-07-26Bibliographically approved
Cattaneo, R., Galin, M. A. & Krasnov, V. M. (2022). Observation of collective excitation of surface plasmon resonances in large Josephson junction arrays. Beilstein Journal of Nanotechnology, 13, 1578-1588
Open this publication in new window or tab >>Observation of collective excitation of surface plasmon resonances in large Josephson junction arrays
2022 (English)In: Beilstein Journal of Nanotechnology, ISSN 2190-4286, Vol. 13, p. 1578-1588Article in journal (Refereed) Published
Abstract [en]

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/NbxSi1−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, Nth ≈ 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.

Keywords
cavity modes, Josephson junctions, synchronization mechanism, THz radiation
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:su:diva-213924 (URN)10.3762/bjnano.13.132 (DOI)000906208900001 ()36636736 (PubMedID)
Available from: 2023-01-18 Created: 2023-01-18 Last updated: 2023-01-18Bibliographically approved
Hovhannisyan, R. A., Kapran, O. M., Golod, T. & Krasnov, V. M. (2021). Accurate Determination of the Josephson Critical Current by Lock-In Measurements. Nanomaterials, 11(8), Article ID 2058.
Open this publication in new window or tab >>Accurate Determination of the Josephson Critical Current by Lock-In Measurements
2021 (English)In: Nanomaterials, E-ISSN 2079-4991, Vol. 11, no 8, article id 2058Article in journal (Refereed) Published
Abstract [en]

Operation of Josephson electronics usually requires determination of the Josephson critical current Ic, which is affected both by fluctuations and measurement noise. Lock-in measurements allow obviation of 1/f noise, and therefore, provide a major advantage in terms of noise and accuracy with respect to conventional dc measurements. In this work we show both theoretically and experimentally that the Ic can be accurately extracted using first and third harmonic lock-in measurements of junction resistance. We derived analytical expressions and verified them experimentally on nano-scale Nb-PtNi-Nb and Nb-CuNi-Nb Josephson junctions.

Keywords
Josephson effect, superconductivity, quantum electronics, nano-devices
National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-197488 (URN)10.3390/nano11082058 (DOI)000690211200001 ()34443889 (PubMedID)
Available from: 2021-10-07 Created: 2021-10-07 Last updated: 2022-01-07Bibliographically approved
Kapran, O. M., Golod, T., Iovan, A., Sidorenko, A. S., Golubov, A. A. & Krasnov, V. M. (2021). Crossover between short- and long-range proximity effects in superconductor/ferromagnet/superconductor junctions with Ni-based ferromagnets. Physical Review B, 103(9), Article ID 094509.
Open this publication in new window or tab >>Crossover between short- and long-range proximity effects in superconductor/ferromagnet/superconductor junctions with Ni-based ferromagnets
Show others...
2021 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 103, no 9, article id 094509Article in journal (Refereed) Published
Abstract [en]

We study superconductor/ferromagnet/superconductor junctions with CuNi, PtNi, or Ni interlayers. Remarkably, we observe that supercurrents through Ni can be significantly larger than through diluted alloys. The phenomenon is attributed to the dirtiness of disordered alloys leading to a short coherence length despite a small exchange energy. To the contrary, pure Ni is clean resulting in a coherence length as long as in a normal metal. Analysis of temperature dependencies of critical currents reveals a crossover from short (dirty) to long (clean) range proximity effects in Pt1−xNix with increasing Ni concentration. Our results point out that structural properties of a ferromagnet play a crucial role for the proximity effect and indicate that conventional strong-but-clean ferromagnets can be advantageously used in superconducting spintronic devices.

National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:su:diva-194535 (URN)10.1103/PhysRevB.103.094509 (DOI)000646411000004 ()2-s2.0-85102849716 (Scopus ID)
Funder
EU, Horizon 2020
Available from: 2021-08-03 Created: 2021-08-03 Last updated: 2022-03-29Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-3131-8658

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