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Golod, Taras
Publications (10 of 28) Show all publications
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
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
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
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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
Kapran, O. M., Morari, R., Golod, T., Borodianskyi, E. A., Boian, V., Prepelita, A., . . . Krasnov, V. M. (2021). In situ transport characterization of magnetic states in Nb/Co superconductor/ferromagnet heterostructures. Beilstein Journal of Nanotechnology, 12, 913-923
Open this publication in new window or tab >>In situ transport characterization of magnetic states in Nb/Co superconductor/ferromagnet heterostructures
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2021 (English)In: Beilstein Journal of Nanotechnology, ISSN 2190-4286, Vol. 12, p. 913-923Article in journal (Refereed) Published
Abstract [en]

Employment of the non-trivial proximity effect in superconductor/ferromagnet (S/F) heterostructures for the creation of novel superconducting devices requires accurate control of magnetic states in complex thin-film multilayers. In this work, we study experimentally in-plane transport properties of microstructured Nb/Co multilayers. We apply various transport characterization techniques, including magnetoresistance, Hall effect, and the first-order-reversal-curves (FORC) analysis. We demonstrate how FORC can be used for detailed in situ characterization of magnetic states. It reveals that upon reduction of the external field, the magnetization in ferromagnetic layers first rotates in a coherent scissor-like manner, then switches abruptly into the antiparallel state and after that splits into the polydomain state, which gradually turns into the opposite parallel state. The polydomain state is manifested by a profound enhancement of resistance caused by a flux-flow phenomenon, triggered by domain stray fields. The scissor state represents the noncollinear magnetic state in which the unconventional odd-frequency spin-triplet order parameter should appear. The non-hysteretic nature of this state allows for reversible tuning of the magnetic orientation. Thus, we identify the range of parameters and the procedure for in situ control of devices based on S/F heterostructures.

Keywords
cryogenic computing, devices exploiting spin polarized transport or integrated magnetic field, spin-valve, superconducting multilayers, superconducting spintronics
National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-197400 (URN)10.3762/bjnano.12.68 (DOI)000686077600001 ()34497739 (PubMedID)2-s2.0-85115887526 (Scopus ID)
Available from: 2021-10-04 Created: 2021-10-04 Last updated: 2022-03-30Bibliographically 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
Kapran, O. M., Iovan, A., Golod, T. & Krasnov, V. M. (2020). Observation of the dominant spin-triplet supercurrent in Josephson spin valves with strong Ni ferromagnets. Physical Review Research, 2(1), Article ID 013167.
Open this publication in new window or tab >>Observation of the dominant spin-triplet supercurrent in Josephson spin valves with strong Ni ferromagnets
2020 (English)In: Physical Review Research, E-ISSN 2643-1564, Vol. 2, no 1, article id 013167Article in journal (Refereed) Published
Abstract [en]

We study experimentally nanoscale Josephson junctions and Josephson spin valves containing strongly ferromagnetic Ni interlayers. We observe that in contrast to junctions, spin valves with the same geometry exhibit anomalous Ic(H) patterns with two peaks separated by a dip. We develop several techniques for in situ characterization of micromagnetic states in our nanodevices, including magnetoresistance, absolute Josephson fluxometry, and first-order-reversal-curves analysis. They reveal a clear correlation of the dip in supercurrent with the antiparallel state of a spin valve and the peaks with two noncollinear magnetic states, thus providing evidence for generation of spin-triplet superconductivity. A quantitative analysis, based on micromagnetic simulations, brings us to the conclusion that the triplet current in our Ni-based spin valves is approximately three times larger than the conventional spin-singlet supercurrent.

Keywords
Superconductivity, Ferromagnetism, spin-triplet state
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:su:diva-203360 (URN)10.1103/physrevresearch.2.013167 (DOI)000602492900006 ()2-s2.0-85091855051 (Scopus ID)
Funder
EU, Horizon 2020, 810144
Available from: 2022-03-29 Created: 2022-03-29 Last updated: 2022-03-29Bibliographically approved
de Andrés Prada, R., Golod, T., Bernhard, C. & Krasnov, V. M. (2019). Growth and Nanofabrication of All-Perovskite Superconducting/Ferromagnetic/Superconducting Junctions. Journal of Superconductivity and Novel Magnetism, 32(9), 2721-2726
Open this publication in new window or tab >>Growth and Nanofabrication of All-Perovskite Superconducting/Ferromagnetic/Superconducting Junctions
2019 (English)In: Journal of Superconductivity and Novel Magnetism, ISSN 1557-1939, E-ISSN 1557-1947, Vol. 32, no 9, p. 2721-2726Article in journal (Refereed) Published
Abstract [en]

We fabricate and study experimentally all-perovskite-oxide superconductor/ferromagnetic insulator/superconductor (S/FI/S) tunnel junctions made out of the high-temperature cuprate superconductor YBa2Cu3O7−y (YBCO) and the colossal magnetoresistive manganite LaMnO3 (LMO) in the ferromagnetic insulator state. YBCO/LMO/YBCO heterostructures with different LMO thicknesses (5, 10, and 20 nm) are grown epitaxially via pulsed laser deposition. Nanoscale S/FI/S junctions with sizes down to 300 nm are made by three-dimensional nano-sculpturing with focused ion beam. Junctions with a thick (20 nm) LMO barrier exhibit a large negative magnetoresistance below TCurie∼160 K, typical for colossal magnetoresistive manganites, as well as a kink in the current-voltage characteristics at large bias (V∼1–2 Volts), attributed to Zener-type tunneling. However, they do not show a measurable Josephson current. On the contrary, junctions with the thinnest 5-nm LMO barrier exhibit a large supercurrent and no signs of magnetism. The latter may indicate the presence of pinholes due to thickness inhomogeneity and/or a ∼ 2 nm dead magnetic layer at the YBCO / LMO interface caused, e.g., by interdiffusion or strain. The junction with an intermediate 10-nm LMO barrier exhibited a desired S/FI/S junction behavior with significant negative magnetoresistance and signatures of a small Josephson current.

Keywords
Perovskites, Josephson junction, Tunnel junction, LMO, YBCO
National Category
Condensed Matter Physics
Research subject
Physics
Identifiers
urn:nbn:se:su:diva-172856 (URN)10.1007/s10948-019-5023-6 (DOI)000491343200003 ()2-s2.0-85062997740 (Scopus ID)
Available from: 2019-09-11 Created: 2019-09-11 Last updated: 2022-03-29Bibliographically approved
de Andrés Prada, R., Golod, T., Kapran, O. M., Borodianskyi, E. A., Bernhard, C. & Krasnov, V. M. (2019). Memory-functionality superconductor/ferromagnet/superconductor junctions based on the high-Tc cuprate superconductors YBa2Cu3O7−x and the colossal magnetoresistive manganite ferromagnets La2/3X1/3MnO3+δ(X=Ca,Sr). Physical Review B, 99(21), Article ID 214510.
Open this publication in new window or tab >>Memory-functionality superconductor/ferromagnet/superconductor junctions based on the high-Tc cuprate superconductors YBa2Cu3O7−x and the colossal magnetoresistive manganite ferromagnets La2/3X1/3MnO3+δ(X=Ca,Sr)
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2019 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 99, no 21, article id 214510Article in journal (Refereed) Published
Abstract [en]

Complex oxides exhibit a variety of unusual physical properties, which can be used for designing novel electronic devices. Here we fabricate and study experimentally nanoscale superconductor/ferromagnet/ superconductor junctions with the high-Tc cuprate superconductors YBa2Cu3O7−x and the colossal magnetoresistive (CMR) manganite ferromagnets La2/3X1/3MnO3+δ(X=CaorSr). We demonstrate that in a broad temperature range the magnetization of a manganite nanoparticle, forming the junction interface, switches abruptly in a monodomain manner. The CMR phenomenon translates the magnetization loop into a hysteretic magnetoresistance loop. The latter facilitates a memory functionality of such a junction with just a single CMR ferromagnetic layer. The orientation of the magnetization (stored information) can be read out by simply measuring the junction resistance in a finite magnetic field. The CMR facilitates a large readout signal in a small applied field. We argue that such a simple single-layer CMR junction can operate as a memory cell both in the superconducting state at cryogenic temperatures and in the normal state up to room temperature.

Keywords
High-temperature superconductivity, collosal magnetoresistance, oxide electronics
National Category
Condensed Matter Physics
Research subject
Physics
Identifiers
urn:nbn:se:su:diva-171104 (URN)10.1103/PhysRevB.99.214510 (DOI)000473009200002 ()2-s2.0-85068618863 (Scopus ID)
Available from: 2019-08-17 Created: 2019-08-17 Last updated: 2022-11-02Bibliographically approved
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