The Experts below are selected from a list of 15750 Experts worldwide ranked by ideXlab platform
Yu N Ovchinnikov - One of the best experts on this subject based on the ideXlab platform.
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singular temperature dependence of the equation of state of superconductors with spin orbit interaction in low temperature region ii
Journal of Superconductivity and Novel Magnetism, 2018Co-Authors: Yu N OvchinnikovAbstract:We extend a previous study of the space and temperature dependence of the order parameter in an ultrathin Superconducting Film in a longitudinal magnetic field to the vicinity of the critical transition surface. In these Films, the spin-orbit interaction can be sizeable. The calculations are restricted to the low-temperature regime. Special attention is given to the zero temperature limit where the state with the maximum value of the critical field is investigated for the given strength of the spin-orbit interaction.
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singular temperature dependence of the equation of state of superconductors with spin orbit interaction in the low temperature region
Journal of Experimental and Theoretical Physics, 2016Co-Authors: Yu N OvchinnikovAbstract:The equation of state is investigated for a thin Superconducting Film in a longitudinal magnetic field and with strong spin-orbit interaction at the critical point. As a first step, the state with the maximal value of the magnetic field for a given value of spin–orbit interaction at T = 0 is chosen. This state is investigated in the low-temperature region. The temperature contribution to the equation of state is weakly singular.
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nucleation of vortices inside open and blind microholes
Physical Review B, 1996Co-Authors: Alexey Bezryadin, Yu N Ovchinnikov, B PannetierAbstract:The critical field of a thin Superconducting Film with a blind circular hole is found theoretically. It is shown that the value of the critical field is sensitive to the bottom thickness, but the orbital momentum, i.e., the number of vortices which nucleate inside the hole, is not sensitive. A simple boundary condition for a steplike thin Film is derived and used for comparative numerical analysis of the superconductivity nucleation in a microdisk and near the hole. By increasing the thickness of the bottom of a blind hole one can transform the hole into a disk of the same radius which rests on top of the Film. We show that such transformation leads to a jump in the number of vortices which nucleate at the critical magnetic field inside the perimeter of the hole (the disk). We report also the results of the Bitter decoration experiments of a thin Superconducting Film with a lattice of open or blind holes. It is found (in accordance with the calculation) that the bottom thickness has only a weak influence on the number of vortices captured by a hole during the cooling of the sample at a constant perpendicular magnetic field. All the experimental results are explained under the assumption that the vortices nucleated inside a hole rest inside during the cooling process and no additional vortices enter the hole. \textcopyright{} 1996 The American Physical Society.
M Bauer - One of the best experts on this subject based on the ideXlab platform.
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anisotropic in plane reversible strain effect in y0 5gd0 5ba2cu3o7 δ coated conductors
Superconductor Science and Technology, 2011Co-Authors: Dmytro Abraimov, Anatolii Polyanskii, David C. Larbalestier, J F Douglas, R. Semerad, D C Van Der Laan, M BauerAbstract:Recent experiments have shown that reversible effects of strain on the critical current density and flux pinning strength in the high-temperature superconductor Bi2Sr2Ca2Cu3Ox can be explained entirely by the pressure dependence of its critical temperature. Such a correlation is less simple for RE–Ba2Cu3O7 − δ (RE = rare earth) superconductors, in part because the in-plane pressure dependence of its critical temperature is highly anisotropic. Here, we make a qualitative correlation between the uniaxial pressure dependence of the critical temperature and the reversible strain effect on the critical current of RE–Ba2Cu3O7 − δ coated conductors by taking the crystallography and texture of the Superconducting Film into account. The strain sensitivity of the critical current is highest when strain is oriented along the [100] and [010] directions of the Superconducting Film, whereas the critical current becomes almost independent of strain when strain is oriented along the [110] direction. The results confirm the important role of the anisotropic pressure dependence of the critical temperature on the reversible strain behavior of RE–Ba2Cu3O7 − δ. The reversible strain effect in RE–Ba2Cu3O7 − δ is expected to decrease the performance of the conductor in many applications, such as high-field magnets, but the effect may be only minor in coated conductor cables, where strain is generally not aligned with the tape axis.
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anisotropic in plane reversible strain effect in y0 5gd0 5ba2cu3o7 δ coated conductors
Superconductor Science and Technology, 2011Co-Authors: Dmytro Abraimov, David C. Larbalestier, J F Douglas, R. Semerad, D C Van Der Laan, A A Polyanskii, M BauerAbstract:Recent experiments have shown that reversible effects of strain on the critical current density and flux pinning strength in the high-temperature superconductor Bi2Sr2Ca2Cu3Ox can be explained entirely by the pressure dependence of its critical temperature. Such a correlation is less simple for RE–Ba2Cu3O7 − δ (RE = rare earth) superconductors, in part because the in-plane pressure dependence of its critical temperature is highly anisotropic. Here, we make a qualitative correlation between the uniaxial pressure dependence of the critical temperature and the reversible strain effect on the critical current of RE–Ba2Cu3O7 − δ coated conductors by taking the crystallography and texture of the Superconducting Film into account. The strain sensitivity of the critical current is highest when strain is oriented along the [100] and [010] directions of the Superconducting Film, whereas the critical current becomes almost independent of strain when strain is oriented along the [110] direction. The results confirm the important role of the anisotropic pressure dependence of the critical temperature on the reversible strain behavior of RE–Ba2Cu3O7 − δ. The reversible strain effect in RE–Ba2Cu3O7 − δ is expected to decrease the performance of the conductor in many applications, such as high-field magnets, but the effect may be only minor in coated conductor cables, where strain is generally not aligned with the tape axis.
Philip Daniel Mauskopf - One of the best experts on this subject based on the ideXlab platform.
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photon noise limited sensitivity in titanium nitride kinetic inductance detectors
Applied Physics Letters, 2015Co-Authors: Johannes Hubmayr, K D Irwin, G C Hilton, J A Beall, D Becker, H M Cho, Mark Devlin, Bradley Dober, Christopher Groppi, Philip Daniel MauskopfAbstract:We demonstrate photon-noise limited performance at sub-millimeter wavelengths in feedhorn-coupled, microwave kinetic inductance detectors made of a TiN/Ti/TiN trilayer Superconducting Film, tuned to have a transition temperature of 1.4 K. Micro-machining of the silicon-on-insulator wafer backside creates a quarter-wavelength backshort optimized for efficient coupling at 250 μm. Using frequency read out and when viewing a variable temperature blackbody source, we measure device noise consistent with photon noise when the incident optical power is >0.5 pW, corresponding to noise equivalent powers >3×10−17 W/Hz. This sensitivity makes these devices suitable for broadband photometric applications at these wavelengths.
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photon noise limited sensitivity in titanium nitride kinetic inductance detectors
arXiv: Instrumentation and Methods for Astrophysics, 2014Co-Authors: Johannes Hubmayr, K D Irwin, G C Hilton, J A Beall, D Becker, H M Cho, Bradley Dober, Christopher Groppi, Mark J Devlin, Philip Daniel MauskopfAbstract:We demonstrate photon-noise limited performance at sub-millimeter wavelengths in feedhorn-coupled, microwave kinetic inductance detectors (MKIDs) made of a TiN/Ti/TiN trilayer Superconducting Film, tuned to have a transition temperature of 1.4~K. Micro-machining of the silicon-on-insulator wafer backside creates a quarter-wavelength backshort optimized for efficient coupling at 250~\micron. Using frequency read out and when viewing a variable temperature blackbody source, we measure device noise consistent with photon noise when the incident optical power is $>$~0.5~pW, corresponding to noise equivalent powers $>$~3$\times 10^{-17}$ W/$\sqrt{\mathrm{Hz}}$. This sensitivity makes these devices suitable for broadband photometric applications at these wavelengths.
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calculation of the characteristics of coplanar resonators for kinetic inductance detectors
IEEE Transactions on Applied Superconductivity, 2005Co-Authors: Adrian Porch, Philip Daniel Mauskopf, S Doyle, C DunscombeAbstract:Photon detectors based on the change of kinetic inductance of a thin Superconducting Film have a number of applications, particularly in astronomy, owing to their high sensitivity and ease of integration into large arrays. Here we discuss in detail the analysis of kinetic inductance detectors that use thin Film microwave coplanar resonators. Photon absorption decreases the electron pair density, increasing the magnetic penetration depth /spl lambda/, which causes a decrease in the resonant frequency (or phase) of an irradiated resonator. To quantify this effect, we first compute the resonator current distribution, from which the /spl lambda/-dependent parameters (such as kinetic inductance) are calculated. Optimum responsivity for phase measurement is achieved by using the thinnest Film with the narrowest center conductor width at the lowest possible temperature. However, the responsivity is compromised by extrinsic microwave losses, in particular due to residual surface resistance, which is likely to be significant in the thinnest Films.
K D Irwin - One of the best experts on this subject based on the ideXlab platform.
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photon noise limited sensitivity in titanium nitride kinetic inductance detectors
Applied Physics Letters, 2015Co-Authors: Johannes Hubmayr, K D Irwin, G C Hilton, J A Beall, D Becker, H M Cho, Mark Devlin, Bradley Dober, Christopher Groppi, Philip Daniel MauskopfAbstract:We demonstrate photon-noise limited performance at sub-millimeter wavelengths in feedhorn-coupled, microwave kinetic inductance detectors made of a TiN/Ti/TiN trilayer Superconducting Film, tuned to have a transition temperature of 1.4 K. Micro-machining of the silicon-on-insulator wafer backside creates a quarter-wavelength backshort optimized for efficient coupling at 250 μm. Using frequency read out and when viewing a variable temperature blackbody source, we measure device noise consistent with photon noise when the incident optical power is >0.5 pW, corresponding to noise equivalent powers >3×10−17 W/Hz. This sensitivity makes these devices suitable for broadband photometric applications at these wavelengths.
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photon noise limited sensitivity in titanium nitride kinetic inductance detectors
arXiv: Instrumentation and Methods for Astrophysics, 2014Co-Authors: Johannes Hubmayr, K D Irwin, G C Hilton, J A Beall, D Becker, H M Cho, Bradley Dober, Christopher Groppi, Mark J Devlin, Philip Daniel MauskopfAbstract:We demonstrate photon-noise limited performance at sub-millimeter wavelengths in feedhorn-coupled, microwave kinetic inductance detectors (MKIDs) made of a TiN/Ti/TiN trilayer Superconducting Film, tuned to have a transition temperature of 1.4~K. Micro-machining of the silicon-on-insulator wafer backside creates a quarter-wavelength backshort optimized for efficient coupling at 250~\micron. Using frequency read out and when viewing a variable temperature blackbody source, we measure device noise consistent with photon noise when the incident optical power is $>$~0.5~pW, corresponding to noise equivalent powers $>$~3$\times 10^{-17}$ W/$\sqrt{\mathrm{Hz}}$. This sensitivity makes these devices suitable for broadband photometric applications at these wavelengths.
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thermal response time of Superconducting transition edge microcalorimeters
Journal of Applied Physics, 1998Co-Authors: K D Irwin, G C Hilton, David A Wollman, John M MartinisAbstract:We investigate limits on the thermal-response time of Superconducting transition-edge microcalorimeters. For operation at 0.1 K, we show that the lower limit on the response time of a Superconducting transition-edge microcalorimeter is of order 1 μs due to the heat diffusion time, electrical instabilities, the amplifier noise, and the critical current of the Superconducting Film. The response time is not limited by self-heating effects and is independent of the intended photon energy. However, design constraints associated with the inductance of the bias circuit make it difficult to achieve the fastest response times for devices with heat capacities high enough for x-ray and gamma-ray detection.
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a Superconducting bolometer with strong electrothermal feedback
Applied Physics Letters, 1996Co-Authors: A T Lee, P L Richards, Sae Woo Nam, B Cabrera, K D IrwinAbstract:We present a theoretical analysis and experimental evaluation of a transition‐edge Superconducting bolometer for detecting infrared and millimeter waves. The Superconducting Film is voltage biased and the current is read by a Superconducting quantum interference device ammeter. Strong electrothermal feedback maintains the sensor temperature within the transition, gives a current responsivity that is simply the inverse of the bias voltage, and reduces the response time by several orders of magnitude below the intrinsic time constant C/G. We evaluated a voltage‐biased bolometer that operates on the Tc∼95 mK transition of a tungsten Film with a thermal conductance of G∼1.2×10−9 W/K. As expected, the electrical noise equivalent power of 3.3×10−17/W√Hz is close to the thermal fluctuation noise limit and is lower than that of other technologies for these values of G and temperature. The measured time constant of 10 μs is ∼100 times faster than the intrinsic time constant.
V V Moshchalkov - One of the best experts on this subject based on the ideXlab platform.
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flux penetration in a Superconducting Film partially capped with a conducting layer
Physical Review B, 2017Co-Authors: Jeremy Brisbois, V V Moshchalkov, V N Gladilin, J Tempere, J T Devreese, F Colauto, M Motta, T H JohansenAbstract:The influence of a conducting layer on the magnetic flux penetration in a Superconducting Nb Film is studied by magneto-optical imaging. The metallic layer partially covering the superconductor provides an additional velocity-dependent damping mechanism for the flux motion that helps to protect the Superconducting state when thermomagnetic instabilities develop. If the flux advances with a velocity slower than omega = 2/mu(0)sigma t, where sigma is the cap layer conductivity and t is its thickness, the flux penetration remains unaffected, whereas for incoming flux moving faster than w, the metallic layer becomes an active screening shield. When the metallic layer is replaced by a perfect conductor, it is expected that the flux braking effect will occur for all flux velocities. We investigate this effect by studying Nb samples with a thickness step. Some of the observed features, namely the deflection of the flux trajectories at the border of the thick center, as well as the favored flux penetration at the indentation, are reproduced by time-dependent Ginzburg-Landau simulations.
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stress overshoot and configuration induced hysteresis in type ii Superconducting Films with a periodic pinning array
Physical Review B, 2008Co-Authors: Qinghua Chen, C Carballeira, Taichiro Nishio, B Y Zhu, V V MoshchalkovAbstract:We have simulated numerically the voltage-current (V-I) characteristics of a type-II Superconducting Film with three different types of periodic magnetic dot arrays. Our findings show that, in the absence of thermal fluctuations, the vortex-vortex and pin interactions vary with the configuration of the dot array. Subsequently, the three systems present different degrees of stress overshoot that give rise to different hysteresis and types of transitions in their V-I curves. The width of the hysteresis can be analytically estimated by using an infinite-range model, which is in good agreement with the simulations.
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anisotropic vortex pinning in superconductors with a square array of rectangular submicron holes
Physical Review B, 2002Co-Authors: L Van Look, B Y Zhu, R Jonckheere, B R Zhao, Z X Zhao, V V MoshchalkovAbstract:We investigate vortex pinning in thin Superconducting Films with a square array of rectangular submicron holes ("antidots"). Two types of antidots are considered: antidots fully perforating the Superconducting Film and "blind antidots," holes that perforate the Film only up to a certain depth. In both systems, we observe a distinct anisotropy in the pinning properties, reflected in the critical current I-c, depending on the direction of the applied electrical current: parallel to the long side of the antidots or perpendicular to it. Although the mechanism responsible for the effect is very different in the two systems, they both show a higher critical current and a sharper I-V transition when the current is applied along the long side of the rectangular antidots.
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local observation of field polarity dependent flux pinning by magnetic dipoles
Physical Review Letters, 2001Co-Authors: M J Van Bael, Joost Bekaert, K Temst, L Van Look, V V Moshchalkov, Y Bruynseraede, G D Howells, A N Grigorenko, S J Bending, G BorghsAbstract:A scanning Hall probe microscope is used to study flux pinning in a thin Superconducting Pb Film covering a square array of single-domain Co dots with in-plane magnetization. We show that single flux quanta of opposite sign thread the Superconducting Film below ${T}_{c}$ at the opposite poles of these dipoles. Depending on the polarity of the applied field, flux lines are attracted to a specific pole of the dipoles, due to the direct interaction with the vortexlike structures induced by the local stray field.
