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## Cooper pair splitting in ballistic ferromagnetic SQUIDs

Cornell University
,
2017.
No. arXiv:1708.05089.

Stroganov P. L., Ya. V. Fominov

We consider ballistic SQUIDs with spin filtering inside half-metallic ferromagnetic arms. A singlet Cooper pair cannot pass through an arm in this case, so the Josephson current is entirely due to the Cooper pair splitting, with two electrons going to different interferometer arms. In order to elucidate the mechanisms of Josephson transport due to split Cooper pairs, we assume the arms to be single-channel wires in the short-junction limit. Different geometries of the system (determined by the length of the arms and the phases acquired by quasiparticles during splitting between the arms) lead to qualitatively different behavior of the SQUID characteristics (the Andreev levels, the current-phase relation, and the critical Josephson current) as a function of two control parameters, the external magnetic flux and misorientation of the two spin filters. The current-phase relation can change its amplitude and shape, in particular, turning to a π-junction form or acquiring additional zero crossings. The critical current can become a nonmonotonic function of the misorientation of the spin filters and the magnetic flux (on half of period). Periodicity with respect to the magnetic flux is doubled, in comparison to conventional SQUIDs.

P. A. Ioselevich, Ostrovsky P. M., Ya. V. Fominov et al., Physical Review B: Condensed Matter and Materials Physics 2017 Vol. 95 No. 9 P. 094508-1-094508-6

We study Josephson junctions with weak links consisting of two parallel disordered arms with magnetic
properties: ferromagnetic, half-metallic, or normal with magnetic impurities. In the case of long links, the
Josephson effect is dominated by mesoscopic fluctuations. In this regime, the system realizes a phi_0 junction with
sample-specific phi_0 and critical current. Cooper pair splitting between the two ...

Added: October 18, 2017

Stroganov P. L., Ya.V. Fominov, Physical Review B: Condensed Matter and Materials Physics 2017 Vol. 96 No. 17 P. 174508-1-174508-13

We consider ballistic SQUIDs with spin filtering inside half-metallic ferromagnetic arms. A singlet Cooper pair
cannot pass through an arm in this case, so the Josephson current is entirely due to the Cooper pair splitting, with
two electrons going to different interferometer arms. In order to elucidate the mechanisms of Josephson transport
due to split Cooper pairs, we ...

Added: November 17, 2017

Fominov Ya.V., Mikhailov D. S., Physical Review B: Condensed Matter and Materials Physics 2022 Vol. 106 No. 13 Article 134514

We theoretically investigate asymmetric two-junction SQUIDs with different current-phase relations in the two Josephson junctions, involving higher Josephson harmonics. Our main focus is on the "minimal model" with one junction in the SQUID loop possessing the sinusoidal current-phase relation and the other one featuring additional second harmonic. The current-voltage characteristic (CVC) turns out to be ...

Added: October 31, 2022

Shein K., Zarudneva A., Emel’yanova V. et al., Physics of the Solid State 2020 Vol. 62 No. 9 P. 1539-1542

The transport properties of two types of quasi-one-dimensional superconducting microstructures were investigated at ultra-low temperatures: the narrow channels close-packed in the shape of meander, and the chains of tunneling contacts "superconductor-insulator-superconductor." Both types of the microstructures demonstrated high value of high-frequency impedance and-or the dynamic resistance. The study opens up potential for using of such ...

Added: September 18, 2020

Arutyunov K., M. : Lebedev Institute, 2017

Superconducting properties of metallic nanowires can be entirely different from those of bulk superconductors because of the dominating role played by thermal and quantum fluctuations of the order parameter. For superconducting channels with diameters below ∼ 50 nm fluctuations of the phase of the complex order parameter - the phase slippage - lead to non-zero ...

Added: October 1, 2017

Гинзбург Л. В., Батов И. Е., Больгинов В. В. et al., Письма в Журнал экспериментальной и теоретической физики 2018 Т. 107 № 1 С. 54- 61

An analytical approach that makes it possible to reconstruct the current–phase relation (CPR) in Josephson
structures included in one of the arms of a two-junction superconducting quantum interference device
(SQUID), where the second junction has a significantly higher critical current and a known (sinusoidal)
CPR, has been developed. The developed methods of analytical and numerical studies of current–flow ...

Added: June 21, 2021

Curran P., Kim J., Satchell N. et al., Applied Physics Letters 2015 Vol. 107 P. 262602-262602

We demonstrate that the magnetic state of a superconducting spin valve, that is normally controlled with an external magnetic field, can also be manipulated by varying the temperature which increases the functionality and flexibility of such structures as switching elements. In this case, switching is driven by changes in the magnetostatic energy due to spontaneous ...

Added: February 22, 2017

Андрияхина Е. С., Burmistrov I., Журнал экспериментальной и теоретической физики 2022 Т. 162 № 4 С. 522-540

The interplay of Anderson localization and electron-electron interactions is known to lead to enhancement of superconductivity due to multifractality of electron wave functions. We develop the theory of multifractally-enhanced superconducting states in two-dimensional systems in the presence of spin-orbit coupling. Using the Finkel'stein nonlinear sigma model, we derive the modified Usadel and gap equations that ...

Added: November 13, 2022

Averin D. V., Wang G., A.S. Vasenko, Physical Review B: Condensed Matter and Materials Physics 2020 Vol. 102 No. 14 P. 144516-1-144516-6

We extend the basic theory of Andreev reflection (AR) in a normal metal/superconductor junction to the situation with an arbitrary time-dependent bias voltage V(t) across the junction. The central element of the theory is the fact that the Fourier transform of the AR amplitude has a casual structure. As an example, the theory is used to describe ...

Added: October 13, 2020

Arutyunov K., Lehtinen J. S., Beilstein Journal of Nanotechnology 2020 Vol. 11 P. 417-420

Chain of superconductor-insulator-superconductor junctions based on Al-AlOx-Al... lift-off fabricated nanostructures was measured at ultra-low temperatures. At zero magnetic field the low current bias dynamic resistance can reach values ~1011 W. The system has been proved to provide a decent quality current biasing circuit enabling observation of Coulomb blockade and Bloch oscillations in ultra-narrow Ti nanowires ...

Added: September 18, 2020

Bubis A. V., E. V. Shpagina, Nasibulin A. G. et al., Physical Review B: Condensed Matter and Materials Physics 2021 Vol. 104 No. 12 Article 125409

We investigate diffusive nanowire-based structures with two normal terminals on the sides and a central
superconducting island in the middle, which is either grounded or floating. Using a semiclassical calculation
we demonstrate that both device layouts permit a quantitative measurement of the energy dependent subgap
thermal conductance Gth from the spectral density of the current noise. In the ...

Added: April 3, 2023

Shapiro D., Mirlin A., Shnirman A., Physical Review B: Condensed Matter and Materials Physics 2021 Vol. 104 No. 3 Article 035434

We consider an interferometer based on artificially induced topological superconductivity and chiral one-dimensional (1D) Majorana fermions. The (nontopological) superconducting island inducing the superconducting correlations in the topological substrate is assumed to be floating. This allows probing the physics of interfering Majorana modes via microwave response, i.e., the frequency-dependent impedance between the island and the earth. ...

Added: October 31, 2021

Golikova T. E., Wolf M. J., Beckmann D. et al., Superconductor Science and Technology 2021 Vol. 34 No. 9 Article 095001

A nonmonotonic dependence of the critical Josephson supercurrent on the injection current
through a normal metal/ferromagnet weak link from a single domain ferromagnetic strip has
been observed experimentally in nanofabricated planar crosslike S-N/F-S Josephson structures.
This behavior is explained by 0–π and π–0 transitions, which can be caused by the suppression
and Zeeman splitting of the induced superconductivity due ...

Added: June 7, 2021

Kamashev A. A., Garif’yanov N. N., Validov A. A. et al., Physical Review B: Condensed Matter and Materials Physics 2019 Vol. 100 P. 134511-1-134511-11

This article represents a mini review of our obtained results about of superconducting spin-valve effect in heterostructures with ferromagnetic Heusler alloy layers.
We have analysed and compared the superconducting properties of the spin-valve structures containing the Heusler alloy Co$_2$Cr$_{1-x}$Fe$_x$Al$_{y}$ as one
of two ferromagnetic (F1 or F2) layers of the F1/F2/S structure, where S stands for the ...

Added: October 25, 2019

T. Karabassov, A.A. Golubov, Silkin V. M. et al., Physical Review B: Condensed Matter and Materials Physics 2021 Vol. 103 P. 224508-1-224508-9

Superconducting hybrid structures with topological order and induced magnetization offer a promising way to realize fault-tolerant quantum computation. However, the effect of the interplay between magnetization and the property of the topological insulator surface, otherwise known as spin-momentum locking on the superconducting proximity effect, still remains to be investigated. We relied on the quasiclassical self-consistent ...

Added: June 4, 2021

Камашев А. А., Гарифьянов Н. Н., Валидов А. А. et al., Физика твердого тела 2022 Т. 64 № 9 С. 1201-1210

Проведен анализ транспортных свойств двух типов спиновых клапанов, в которых в качестве одного из двух ферромагнитных слоев в структурах Ф1/Ф2/C использовался сплав Гейслера Co_{2}Cr_{1−x}Fe_{x}Al_{y}. Слой сплава Гейслера был использован: 1) в качестве слабого ферромагнетика, в случае Ф2-слоя; 2) в качестве полуметалла, в случае Ф1-слоя. В первом случае, был получен большой классический эффект сверхпроводящего спинового клапана ...

Added: October 31, 2022

Arutyunov K., Lehtinen J. S., Radkevich A. A. et al., Journal of Magnetism and Magnetic Materials 2018 Vol. 459 P. 356-358

Quasi-one-dimensional superconducting channels host sound-like plasma modes propagating along the
which are associated with fluctuations of the phase of the superconducting order parameter (Mooiji and
1985) [5]. Interaction between these electromagnetic excitations and charge carriers affects the electron density
of states (DOS). I-V characteristics of tunnel S1-I-S2 junctions, where superconducting S2 electrode
nanowire in the regime of quantum fluctuations ...

Added: October 1, 2017

П.А.Иоселевич, Чукланов Д. А., Письма в Журнал экспериментальной и теоретической физики 2021 Т. 113 № 10 С. 661-668

Рассматривается длинный диффузный контакт Джозефсона, слабой связью в котором является тонкий бислой нормальный металл (N)–ферромагнетик (F), так что N и F образуют параллельные связи между сверхпроводниками S. Показано, что сверхпроводимость в такой слабой связи описывается эффективным одномерным уравнением Узаделя, содержащим ослабленное обменное поле, а также распаривающий член. Механизм распаривания основан на неотъемлемой неоднородности бислоя и ...

Added: October 25, 2021

Denisov A., Bubis A., Piatrusha S. et al., Nanomaterials 2022 Vol. 12 No. 9 Article 1461

Mesoscopic superconductivity deals with various quasiparticle excitation modes, only one of them—the charge-mode—being directly accessible for conductance measurements due to the imbalance in populations of quasi-electron and quasihole excitation branches. Other modes carrying heat or even spin, valley etc. currents populate the branches equally and are charge-neutral, which makes them much harder to control. This ...

Added: April 3, 2023

Temu E., Lahteenmaki P., Golubev D. et al., Journal of Low Temperature Physics 2017 Vol. 189 P. 204-216

We have employed noise thermometry for investigations of thermal relaxation
between the electrons and the substrate in nanowires patterned from 40-nm-thick
titanium film on top of silicon wafers covered by a native oxide. By controlling the
electronic temperature Te by Joule heating at the base temperature of a dilution refrigerator,
we probe the electron–phonon coupling and the thermal boundary ...

Added: December 5, 2017

M. : Faculty of Physics, MSU, 2017

The Low Temperature Physics Conference is an international event held every three years, under the auspices of the IUPAP through its Commission C5 on Low Temperature Physics. The aim of these conferences is to exchange information and views among the members of the international scientific community in the general field of Low Temperature Physics. It ...

Added: October 1, 2017

P. M. Marychev, Vodolazov D. Y., Physical Review B: Condensed Matter and Materials Physics 2022 Vol. 105 No. 9 Article 094522

We theoretically predict that the critical current Ic and magnetization M of a hybrid superconductor/normal-metal (SN) strip may have nonmonotonous dependence on a perpendicular magnetic field—so-called peak effect. In contrast to familiar peak effect, which is connected either with vortex entry to the superconductor or with peculiarities of vortex pinning, the found phenomenon exists at ...

Added: January 13, 2023

Ioselevich P., Chuklanov D. A., JETP Letters 2021 Vol. 113 P. 631-637

We consider a long diffusive Josephson junction where the weak link is a thin (normal metal (N)–ferromagnet (F)) bilayer (N and F form parallel links between superconductors (Ss)). We show that superconductivity in the weak link can be described by an effective one-dimensional Usadel equation containing a “diluted” exchange field as well as a weak ...

Added: October 25, 2021

Марычев П. М., Водолазов Д. Ю., Journal of Physics: Condensed Matter 2021 Vol. 33 No. 38 P. 385301

We have calculated kinetic inductance Lk of a thin superconductor/ferromagnet/normal metal strip in an in-plane Fulde–Ferrell (FF) state. We consider range of parameters when FF state appears at temperature TFF < Tc (Tc is a transition temperature to superconducting state) when the paramagnetic response of FN layers overcomes the diamagnetic response of S layer. We ...

Added: January 12, 2023