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Hovhannisyan, Razmik A.
Publications (6 of 6) Show all publications
Hovhannisyan, R. A., Golod, T. & Krasnov, V. M. (2023). Superresolution magnetic imaging by a Josephson junction via holographic reconstruction of I c ( H ) modulation. Physical Review Applied, 20(6), Article ID 064012.
Open this publication in new window or tab >>Superresolution magnetic imaging by a Josephson junction via holographic reconstruction of I c ( H ) modulation
2023 (English)In: Physical Review Applied, E-ISSN 2331-7019, Vol. 20, no 6, article id 064012Article in journal (Refereed) Published
Abstract [en]

This work provides a proof -of -concept for superresolution magnetic imaging using a single Josephson junction. The technique resembles digital holography: magnetic patterns are obtained via an inverseproblem solution from diffractionlike modulation of the junction's critical current, I c (H) . We demonstrate numerical reconstruction of complex two-dimensional patterns, verify the technique experimentally using Nb-based planar junctions, and fabricate an operational sensor on a cantilever. Our results show that Josephson holography allows for both high spatial resolution (approximately 20 nm) and high field sensitivity (approximately 10 - 11 T R root Hz), thus resolving the trade-off problem between resolution and sensitivity in magnetic scanning probe imaging.

National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:su:diva-231267 (URN)10.1103/PhysRevApplied.20.064012 (DOI)001236593700001 ()2-s2.0-85179626915 (Scopus ID)
Available from: 2024-06-19 Created: 2024-06-19 Last updated: 2024-06-19Bibliographically 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
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
Hovhannisyan, R. A., Grebenchuk, S. Y., Baranov, D. S., Roditchev, D. & Stolyarov, V. S. (2021). Lateral Josephson Junctions as Sensors for Magnetic Microscopy at Nanoscale. The Journal of Physical Chemistry Letters, 12(51), 12196-12201
Open this publication in new window or tab >>Lateral Josephson Junctions as Sensors for Magnetic Microscopy at Nanoscale
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2021 (English)In: The Journal of Physical Chemistry Letters, E-ISSN 1948-7185, Vol. 12, no 51, p. 12196-12201Article in journal (Refereed) Published
Abstract [en]

Lateral Josephson junctions (LJJ) made of two superconducting Nb electrodes coupled by Cu-film are applied to quantify the stray magnetic field of Co-coated cantilevers used in magnetic force microscopy (MFM). The interaction of the magnetic cantilever with LJJ is reflected in the electronic response of LJJ as well as in the phase shift of cantilever oscillations, simultaneously measured. The phenomenon is theorized and used to establish the spatial map of the stray field. Based on our findings, we suggest integrating LJJs directly on the tips of cantilevers and using them as nanosensors of local magnetic fields in scanning probe microscopes. Such probes are less invasive than conventional magnetic MFM cantilevers and simpler to realize than SQUID-on-tip sensors.

Keywords
Sensors, Fluxes, Oscillation, Magnetic properties, Probes
National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-200526 (URN)10.1021/acs.jpclett.1c03556 (DOI)000734278800001 ()34918928 (PubMedID)2-s2.0-85121927286 (Scopus ID)
Available from: 2022-01-10 Created: 2022-01-10 Last updated: 2024-07-04Bibliographically approved
Golod, T., Hovhannisyan, R. A., Kapran, O. M., Dremov, V. V., Stolyarov, V. S. & Krasnov, V. M. (2021). Reconfigurable Josephson Phase Shifter. Nano Letters, 21(12), 5240-5246
Open this publication in new window or tab >>Reconfigurable Josephson Phase Shifter
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2021 (English)In: Nano Letters, ISSN 1530-6984, E-ISSN 1530-6992, Vol. 21, no 12, p. 5240-5246Article in journal (Refereed) Published
Abstract [en]

Phase shifter is one of the key elements of quantum electronics. In order to facilitate operation and avoid decoherence, it has to be reconfigurable, persistent, and nondissipative. In this work, we demonstrate prototypes of such devices in which a Josephson phase shift is generated by coreless superconducting vortices. The smallness of the vortex allows a broad-range tunability by nanoscale manipulation of vortices in a micron-size array of vortex traps. We show that a phase shift in a device containing just a few vortex traps can be reconfigured between a large number of quantized states in a broad [−3π, +3π] range.

Keywords
superconductivity, Josephson junctions, Abrikosov vortices, cryo-electronics
National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-196183 (URN)10.1021/acs.nanolett.1c01366 (DOI)000668003400045 ()34114467 (PubMedID)
Available from: 2021-09-07 Created: 2021-09-07 Last updated: 2022-02-25Bibliographically approved
Karelina, L. N., Hovhannisyan, R. A., Golovchanskiy, I. A., Chichkov, V., Ben Hamida, A., Stolyarov, V. S., . . . Ryazanov, V. V. (2021). Scalable memory elements based on rectangular SIsFS junctions. Journal of Applied Physics, 130(17), Article ID 173901.
Open this publication in new window or tab >>Scalable memory elements based on rectangular SIsFS junctions
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2021 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 130, no 17, article id 173901Article in journal (Refereed) Published
Abstract [en]

We explore the concept of the Josephson magnetic memory element based on a multilayer two-barrier SIsFS Josephson junction storing the digital state by means of the orientation of magnetization in the F-layer. A diluted PdFe alloy with 1% magnetic atoms is used as a ferromagnet (F), and a tunnel A1Ox layer (I) ensures a high voltage in the resistive state. We have studied two junctions of a rectangular shape in which two digital states are defined by the orientation of the residual F-layer magnetization set along or across the junction in the plane of the ferromagnetic barrier. Implementations of both binary and ternary logic elements are demonstrated. A scalability of rectangular memory elements is analyzed using micro-magnetic modeling.

National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-200704 (URN)10.1063/5.0063274 (DOI)000716415500006 ()2-s2.0-85118802432 (Scopus ID)
Available from: 2022-01-11 Created: 2022-01-11 Last updated: 2022-11-11Bibliographically approved
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