Anomalous superconductivity and superfluidity in repulsive fermion systems
Physics-Uspekhi. 2015. Vol. 58. No. 8. P. 733-761.
Kagan M.Yu., Mitskan V. A., Korovushkiin M. M.
We discuss the mechanisms of unconventional super-conductivity and superfluidity in 3D and 2D fermionic systems with purely repulsive interaction at low densities.We construct phase diagrams of these systems and find the areas of the superconducting state in free space, as well as on the lattice in the framework of the Fermi-gas model with hard-core repul- sion, the Hubbard model, the Shubin±Vonsovsky model, and the t-J model. We demonstrate that the critical superconducting temperature can be greatly increased in the spin-polarized case or in a two-band situation already at low densities.
Research target: Physics
Priority areas: engineering science
, , et al., Physical Review B: Condensed Matter and Materials Physics 2016 Vol. 94 No. 18 P. 180508-1-180508-5
We demonstrate coherent dynamics of quantized magnetic fluxes in a superconducting loop with a weak link, a nanobridge patterned from the same thin NbN film as the loop. The bridge is a short, rounded shape constriction, close to 10 nm long and 20–30 nm wide, having minimal width at its center. It superposes neighboring fluxoid ...
Added: February 2, 2017
, , et al., Physica Status Solidi - Rapid Research Letters 2019 No. 1800317 P. 1-5
Quantum confinement is known to affect a nanosized superconductor through quantum-size variations of the electronic density of states. Here, it is demonstrate that there is another quantum-confinement mechanism overlooked in previous studies. In particular, it is found that the electron–electron attraction can be enhanced due to quantum-confinement modifications of electronic wave functions. The superconducting correlations are strengthened by such quantum ...
Added: January 18, 2019
, , et al., IEEE Transactions on Applied Superconductivity 2019 Vol. 29 No. 3 P. 6900505-1-5
The FeSe wires and tapes with Fe (S22 steel) and Cu/Nb sheath were fabricated by various modifications of the powder-in-tube (PIT) method. The superconducting critical parameters (upper critical field, critical current, critical temperature) depending on heat treatment time were investigated using resistive R(T) and transport measurements I (V) in magnetic fields up to 9T. The low-temperature ...
Added: November 26, 2019
, , et al., Russian Journal of Mathematical Physics 2010 Vol. 17 No. 2 P. 154-158
The thermodynamical potential of a superconducting quantum cylinder is calculated. The dependence of the critical temperature and the heat capacity of a superconducting system of the surface concentration of electrons and on the radius of the nanotube is studied. ...
Added: April 12, 2012
, , , Известия Уфимского научного центра РАН 2021 № 1 С. 106-110
This research was performed using thin superconducting strips in the shape of tightly packed meanders made of niobium nitride (NbN) ultrathin superconducting strips about 100 nm wide, 5 nm thick and up to 100 μm long. The structures revealed the effect of high kinetic inductance at temperatures lower than the critical temperature. Consideration was given to the temperature ...
Added: May 27, 2021
Development of the experimental setup for investigation of latching of superconducting single-photon detector caused by blinding attack on the quantum key distribution system
, , et al., EPJ Web of Conferences 2017 Vol. 132 P. 1-2
Recently bright-light control of the SSPD has been demonstrated. This attack employed a "backdoor" in the detector biasing scheme. Under bright-light illumination, SSPD becomes resistive and remains "latched" in the resistive state even when the light is switched off. While the SSPD is latched, Eve can simulate SSPD single-photon response by sending strong light pulses, ...
Added: October 13, 2017
, , Physical Review B: Condensed Matter and Materials Physics 2018 Vol. 97 No. 14 P. 144517-1-144517-16
We study the effect of superconducting fluctuations on the conductivity of metals at arbitrary temperatures T and impurity scattering rates τ−1. Using the standard diagrammatic technique but in the Keldysh representation, we derive the general expression for the fluctuation correction to the dc conductivity applicable for any space dimensionality and analyze it in the case of the film ...
Added: June 6, 2018
, , et al., New Journal of Physics 2020 Vol. 22 No. June Article 063049
In a superconductor that lacks inversion symmetry, the spatial part of the Cooper pair wave function has a reduced symmetry, allowing for the mixing of spin-singlet and spin-triplet Cooper pairing channels and thus providing a pathway to a non-trivial superconducting state. Materials with a non-centrosymmetric crystal structure and with strong spin–orbit coupling are a platform ...
Added: October 11, 2020
, , et al., Physical Review Applied 2019 Vol. 12 No. 5 P. 1-10
We analyze the evolution of the normal and superconducting properties of epitaxial TiN films, characterized by high Ioffe-Regel parameter values, as a function of the film thickness. As the film thickness decreases, we observe an increase of the residual resistivity, that becomes dominated by diffusive surface scattering for d≤20nm. At the same time, a substantial thickness-dependent ...
Added: October 10, 2019
, , et al., Scientific Reports 2017 Vol. 7 No. 1 P. 1-9
While single photon detectors provide superior intensity sensitivity, spectral resolution is usually lost after the detection event. Yet for applications in low signal infrared spectroscopy recovering information about the photon's frequency contributions is essential. Here we use highly efficient waveguide integrated superconducting single-photon detectors for on-chip coherent detection. In a single nanophotonic device, we demonstrate ...
Added: October 13, 2017
, , et al., Физика твердого тела 2019 Т. 61 № 9 С. 1609-1613
Экспериментально исследовались высококачественные пленки алюминия на подложках из GaAs. Был обнаружен заметный рост критической температуры сверхпроводящего перехода с уменьшением толщины пленки. Эффект интерпретируется как проявление квантового размерного эффекта, влияющего как на плотность состояний электронов, так и на электрон-фононное взаимодействие. ...
Added: September 14, 2019
, , et al., Письма в Журнал экспериментальной и теоретической физики 2020 Т. 111 № 3 С. 166-172
Структурная причина сверхпроводимости в допированном атомами Cu, Sr, или Nb топологическом изоляторе Bi2Se3 на сегодняшний день не понятна. Для продвижения в ее понимании в данной работе был реализован подход ко-допирования, и выращены монокристаллы BaySrxBi2Se3 с различными x и y. Изучался состав, структурные и транспортные свойства полученных кристаллов. На основе рентгеновских данных показано, что барий и стронций интеркалируют систему, при том ...
Added: January 25, 2020
, , Physical Review B: Condensed Matter and Materials Physics 2015 Vol. 91 No. 2 P. 024505-1-024505-10
We demonstrate that in sufficiently long diffusive superconducting-normal-superconducting (SNS) junctions dc Josephson current is exponentially suppressed by electron-electron interactions down to zero temperature. This suppression is caused by the effect of Cooper pair dephasing which occurs in the normal metal and defines a new fundamental length scale Lφ in the problem. This length is fully consistent with that derived ...
Added: March 11, 2015
Fast and Sensitive Terahertz Direct Detector Based on Superconducting Antenna-Coupled Hot Electron Bolometer
, , et al., IEEE Transactions on Applied Superconductivity 2015 Vol. 25 No. 3 P. 1-4
We characterize superconducting antenna-coupled hot-electron bolometers for direct detection of terahertz radiation operating at a temperature of 9.0 K. The estimated value of responsivity obtained from lumped-element theory is strongly different from the measured one. A numerical calculation of the detector responsivity is developed, using the Euler method, applied to the system of heat balance ...
Added: March 27, 2015
, , 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
, , Physical Review B: Condensed Matter and Materials Physics 2013 Vol. 88 No. 5 P. 054505-1-054505-10
We investigate the effect of interacting quantum phase slips on persistent current and its fluctuations in ultrathin superconducting nanowires and nanorings pierced by the external magnetic flux. We derive the effective action for these systems and map the original problem onto an effective sine-Gordon theory on torus. We evaluate both the flux dependent persistent current ...
Added: February 9, 2015
, , , Physical Review B: Condensed Matter and Materials Physics 2012 Vol. 86 No. 14 P. 144529-1-144529-5
We argue that electron-electron interactions fundamentally restrict the penetration length of Cooper pairs into a diffusive normal metal from a superconductor. At low temperatures, this Cooper pair dephasing length remains finite and does not diverge. We evaluate the subgap conductance of hybrids in the presence of electron-electron interactions and demonstrate that this length Lϕ can ...
Added: February 9, 2015
Вычисление линейных по мощности поправок к спектральным функциям сверхпроводника и их вклада в отклик сверхпроводниковых детекторов излучения
, , et al., Журнал радиоэлектроники 2011 № 11
We investigate contribution to the detectivity of superconducting radiation sensors, originated from a change in spectral functions of the absorber under influence of the absorbed power. For the absorber manufactured of dirty superconducting film we demonstrate that at low temperature the only cause of the change in spectral functions is the change of the order ...
Added: October 12, 2017
Вывод уравнения типа уравнения Гинзбурга-Ландау для нанопроволоки вблизи критического магнитного поля
, , et al., Журнал радиоэлектроники 2011 № 11
Nonlinear Ginzburg-Landau equation for dirty supercondicting 1D wire is derived in the limit of high magnetic field. ...
Added: October 12, 2017
, , et al., Physical Review B: Condensed Matter and Materials Physics 2013 Vol. 88 P. 220506-1-220506-5
We demonstrate evidence of coherent magnetic flux tunneling through superconducting nanowires patterned in a thin highly disordered NbN film. The phenomenon is revealed as a superposition of flux states in a fully metallic superconducting loop with the nanowire acting as an effective tunnel barrier for the magnetic flux, and reproducibly observed in different wires. The ...
Added: March 13, 2014
Coexistence of superconductivity and spin-density wave in (TMTSF)2ClO4: Spatial structure of the two-phase state
, , et al., Physical Review B: Condensed Matter and Materials Physics 2014 Vol. 89 No. 5 P. 054518-1-054518-10
We report comprehensive (magneto)transport studies of the two-phase state in (TMTSF)2ClO4, where superconducting (SC) phase coexists with spin-density wave insulator (SDW). By tuning the degree of ClO4 anion ordering in controlled manner we smoothly suppress the SDWstate and study resulting evolution of the SC phase spatial texture.We find that as SDWis suppressed, SC regions initially appear inside the ...
Added: March 14, 2016
, , et al., The Journal of Physical Chemistry Letters 2020 Vol. 11 No. 21 P. 9393-9399
In pnictide RbEuFe4As4, superconductivity sets in at 36 K and coexists, below 15−19 K, with the long-range magnetic ordering of Eu 4f spins. Here we report scanning tunneling experiments performed on cold-cleaved single crystals of the compound. The data revealed the coexistence of large Rb-terminated and small Eu-terminated terraces, both manifesting 1 × 2 and ...
Added: October 24, 2020
, , et al., Quasi-1-Dimensional Superconductivity in Highly Disordered NbN Nanowires / . 2016.
The topic of superconductivity in strongly disordered materials has attracted a significant attention. In particular vivid debates are related to the subject of intrinsic spatial inhomogeneity responsible for non-BCS relation between the superconducting gap and the pairing potential. Here we report experimental study of electron transport properties of narrow NbN nanowires with effective cross sections ...
Added: March 22, 2016
, Физика в школе 2015 № 8 С. 49-53
The article treats of one of the current trends of microelectronics, which can be a basis for creation of elective courses or project studies of the students. The article gives the basic theoretical principles and practical applications ...
Added: October 19, 2016