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Journal articles on the topic 'Niobium superconductor'

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Author: Grafiati

Published: 6 September 2023

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1

Senevirathne, I. H., A. Gurevich, and J. R. Delayen. "Direct current magnetic Hall probe technique for measurement of field penetration in thin film superconductors for superconducting radio frequency resonators." Review of Scientific Instruments 93, no. 5 (May 1, 2022): 055104. http://dx.doi.org/10.1063/5.0083309.

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Superconducting Radio Frequency (SRF) cavities used in particle accelerators are typically formed from or coated with superconducting materials. Currently, high purity niobium is the material of choice for SRF cavities that have been optimized to operate near their theoretical field limits. This brings about the need for significant R & D efforts to develop next generation superconducting materials that could outperform Nb and keep up with the demands of new accelerator facilities. To achieve high quality factors and accelerating gradients, the cavity material should be able to remain in the superconducting Meissner state under a high RF magnetic field without penetration of quantized magnetic vortices through the cavity wall. Therefore, the magnetic field at which vortices penetrate a superconductor is one of the key parameters of merit of SRF cavities. Techniques to measure the onset of magnetic field penetration on thin film samples need to be developed to mitigate the issues with the conventional magnetometry measurements that are strongly influenced by the film orientation and shape and edge effects. In this work, we report the development of an experimental setup to measure the field of full flux penetration through films and multi-layered superconductors. Our system combines a small superconducting solenoid that can generate a magnetic field of up to 500 mT at the sample surface and three Hall probes to detect the full flux penetration through the superconductor. This setup can be used to study alternative materials that could potentially outperform niobium, as well as superconductor–insulator–superconductor (SIS) multilayer coatings on niobium.

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2

Malisa, Anayesu B. "Josephson Effect in MgB2/Pd/Nb Trilayer Josephson Junctions." Tanzania Journal of Science 47, no. 3 (August 14, 2021): 1062–72. http://dx.doi.org/10.4314/tjs.v47i3.17.

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This paper reports fabrication techniques and results of MgB2/Pd/Nb trilayer Josephson junctions. The MgB2 bottom electrode was co-evaporated by molecular beam epitaxy (MBE) technique from both magnesium and boron sources at a low substrate temperature ~ 300 °C, while the interlayer and the top niobium electrode (Pd/Nb bilayer) were deposited ex-situ using RF sputtering. The junctions exhibited and Josephson effect as well as a modulation of the critical current in a magnetic field applied in a direction normal to the junction plane. Fractional and integer Shapiro steps were observed at voltages corresponding to the frequency of the applied microwave radiation field. The products of the junctions compare well with the previously reported values. The results suggest that it should be possible to fabricate all-MgB2 and MgB2 as one of the electrodes Superconductor/Normal/Superconductor (SNS), Superconductor/Insulator/Superconductor (SIS) or even Superconductor/Ferromagnet/Superconductor (SFS) tunnel junctions with interesting characteristics and for various applications. Keywords: MgB2; all-MgB2; Josephson Tunnel junctions; trilayer devices; Niobium

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3

Burnell, G., E. J. Tarte, W. E. Booij, and M. G. Blamire. "Niobium-copper superconductor-normal metal-superconductor asymmetry modulated SQUIDs." IEEE Transactions on Appiled Superconductivity 11, no. 1 (March 2001): 1243–46. http://dx.doi.org/10.1109/77.919575.

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4

Yoshida, T., H. Kasai, J. E. Bonevich, T. Matsuda, and A. Tonomura. "Lorentz microscopy observation of vortex dynamics due to transport current." Proceedings, annual meeting, Electron Microscopy Society of America 53 (August 13, 1995): 366–67. http://dx.doi.org/10.1017/s0424820100138208.

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At present, Lorentz microscopy is the only one method to visualize individual vortices in superconductors and observe their motion in real time. Using this technique, we have investigated the fascinating vortex dynamics in superconductors, niobium and BSCCO. And recently we applied it to investigate current driven vortex motion.The vortices are driven by the Lorentz force due to the transport current, and begin to move. This couses the vortex to dissipate the energy i.e., causes the resistive state in the superconductor. Therefore to clarify the vortex motion is important especially in the relation with vortex pinning.The sample we examined was niobium thin film, which was single-crystallized by annealing and thinned by chemical etching. It was put in the low temperature specimen stage specially developed for the vortex observation, which was installed in 350 kV FE-TEM based Hitachi H-9000.We observed current driven vortex motion in the temperature (T) range from 4.5 K to Tc = 9.25 K and in a (externally applied) magnetic field (B) up to 100 Gauss.

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5

Devarakonda, A., H. Inoue, S. Fang, C. Ozsoy-Keskinbora, T. Suzuki, M. Kriener, L. Fu, E. Kaxiras, D. C. Bell, and J. G. Checkelsky. "Clean 2D superconductivity in a bulk van der Waals superlattice." Science 370, no. 6513 (October 8, 2020): 231–36. http://dx.doi.org/10.1126/science.aaz6643.

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Advances in low-dimensional superconductivity are often realized through improvements in material quality. Apart from a small group of organic materials, there is a near absence of clean-limit two-dimensional (2D) superconductors, which presents an impediment to the pursuit of numerous long-standing predictions for exotic superconductivity with fragile pairing symmetries. We developed a bulk superlattice consisting of the transition metal dichalcogenide (TMD) superconductor 2H-niobium disulfide (2H-NbS2) and a commensurate block layer that yields enhanced two-dimensionality, high electronic quality, and clean-limit inorganic 2D superconductivity. The structure of this material may naturally be extended to generate a distinct family of 2D superconductors, topological insulators, and excitonic systems based on TMDs with improved material properties.

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6

Leone, B., B. D. Jackson, J. R. Gao, and T. M. Klapwijk. "Geometric heat trapping in niobium superconductor–insulator– superconductor mixers due to niobium titanium nitride leads." Applied Physics Letters 76, no. 6 (February 7, 2000): 780–82. http://dx.doi.org/10.1063/1.125893.

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7

Soreau-Leblanc, A., P. Molinie´, and J. C. Jumas. "A new tin niobium selenide superconductor." Physica C: Superconductivity 282-287 (August 1997): 741–42. http://dx.doi.org/10.1016/s0921-4534(97)00382-1.

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8

Brems, Xaver S., Sebastian Mühlbauer, Wilmer Y. Córdoba-Camacho, Arkady A. Shanenko, Alexei Vagov, José Albino Aguiar, and Robert Cubitt. "Current-induced self-organisation of mixed superconducting states." Superconductor Science and Technology 35, no. 3 (January 20, 2022): 035003. http://dx.doi.org/10.1088/1361-6668/ac455e.

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Abstract Small-angle neutron scattering is used in combination with transport measurements to investigate the current-induced effects on the morphology of the intermediate mixed state (IMS) domains in the intertype superconductor niobium. We report the robust self-organisation of the vortex lattice domains to elongated parallel stripes perpendicular to the applied current in a steady-state. The experimental results for the formation of the superstructure are supported by theoretical calculations, which highlight important details of the vortex matter evolution. The investigation demonstrates a mechanism of a spontaneous pattern formation that is closely related to the universal physics governing the IMS in low-κ superconductors.

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9

Ogitsu, Toru, Masami Iio, Naritoshi Kawamura, and Makoto Yoshida. "Development of Radiation-Tolerant HTS Magnet for Muon Production Solenoid." Instruments 4, no. 4 (October 12, 2020): 30. http://dx.doi.org/10.3390/instruments4040030.

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Superconducting magnets are widely used in accelerator science applications. Muon production solenoids are applications that have recently attracted considerable public attention, after the approval of muon-related physics projects such as coherent muon to electron transition or muon-to-electron-conversion experiments. Based on its characteristics, muon production solenoids tend to be subjected to high radiation exposure, which results in a high heat load being applied to the solenoid magnet, thus limiting the superconducting magnet operation, especially for low-temperature superconductors such as niobium titanium alloy. However, the use of high-temperature superconductors may extend the operation capabilities owing to their functionality at higher temperatures. This study reviews the characteristics of high temperature superconductor magnets in high-radiation environments and their potential for application to muon production solenoids.

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10

de Matos, Clovis Jacinto, and Christian Beck. "Possible Measurable Effects of Dark Energy in Rotating Superconductors." Advances in Astronomy 2009 (2009): 1–10. http://dx.doi.org/10.1155/2009/931920.

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We discuss recent laboratory experiments with rotating superconductors and show that three so far unexplained experimentally observed effects (anomalous acceleration signals, anomalous gyroscope signals, Cooper pair mass excess) can be physically explained in terms of a possible interaction of dark energy with Cooper pairs. Our approach is based on a Ginzburg-Landau-like model of electromagnetic dark energy, where gravitationally active photons obtain mass in the superconductor. We show that this model can account simultaneously for the anomalous acceleration and anomalous gravitomagnetic fields around rotating superconductors measured by Tajmar et al. and for the anomalous Cooper pair mass in superconductive Niobium, measured by Cabrera and Tate. It is argued that these three different physical effects are ultimately different experimental manifestations of the simultaneous spontaneous breaking of gauge invariance and of the principle of general covariance in superconductive materials.

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11

Laverick, C., and J. K. Hulm. "Niobium demand for superconductor applications: 1988-98." IEEE Transactions on Magnetics 24, no. 2 (March 1988): 998–1002. http://dx.doi.org/10.1109/20.11396.

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12

Laverick, Charles. "Niobium demand and superconductor applications: An overview." Journal of the Less Common Metals 139, no. 1 (April 1988): 107–22. http://dx.doi.org/10.1016/0022-5088(88)90334-7.

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13

Idczak, Rafał, Wojciech Nowak, Bartosz Rusin, Rafał Topolnicki, Tomasz Ossowski, Michał Babij, and Adam Pikul. "Enhanced Superconducting Critical Parameters in a New High-Entropy Alloy Nb0.34Ti0.33Zr0.14Ta0.11Hf0.08." Materials 16, no. 17 (August 24, 2023): 5814. http://dx.doi.org/10.3390/ma16175814.

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The structural and physical properties of the new titanium- and niobium-rich type-A high-entropy alloy (HEA) superconductor Nb0.34Ti0.33Zr0.14Ta0.11Hf0.08 (in at.%) were studied by X-ray powder diffraction, energy dispersive X-ray spectroscopy, magnetization, electrical resistivity, and specific heat measurements. In addition, electronic structure calculations were performed using two complementary methods: the Korringa–Kohn–Rostoker Coherent Potential Approximation (KKR-CPA) and the Projector Augmented Wave (PAW) within Density Functional Theory (DFT). The results obtained indicate that the alloy exhibits type II superconductivity with a critical temperature close to 7.5 K, an intermediate electron–phonon coupling, and an upper critical field of 12.2(1) T. This finding indicates that Nb0.34Ti0.33Zr0.14Ta0.11Hf0.08 has one of the highest upper critical fields among all known HEA superconductors.

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14

Dubitsky, Gennadi A., Vladimir D. Blank, Sergei G. Buga, Elena E. Semenova, Nadejda R. Serebryanaya, Vladimir V. Aksenenkov, Vyatcheslav M. Prokhorov, Vladimir A. Kul’bachinski, Aleksei V. Krechetov, and Vladimir G. Kytin. "Superhard Superconductor Composites Obtained by Sintering of Diamond, c-BN and C60 Powders with Superconductors." Zeitschrift für Naturforschung B 61, no. 12 (December 1, 2006): 1541–46. http://dx.doi.org/10.1515/znb-2006-1210.

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Superhard superconducting samples with a critical temperature of TC = 10.5 - 12.6 K were obtained by high-pressure / high-temperature sintering of synthetic diamond powders coated with a niobium film and in 50% - 50% composition with superhard C60 fullerene. Superhard superconductors with TC = 9.3 K were obtained when diamond and molybdenum powders were sintered at a pressure of 7.7 GPa and a temperature of 2173 K. Superconducting samples with TC = 36.1 - 37.5 K have been obtained in the systems diamond-MgB2 and cubic boron nitride-MgB2.

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15

Raine, Mark J., and Damian P. Hampshire. "Characterization of the Low Temperature Superconductor Niobium Carbonitride." IEEE Transactions on Applied Superconductivity 21, no. 3 (June 2011): 3138–41. http://dx.doi.org/10.1109/tasc.2010.2095491.

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16

Becker, Th, M. Mück, and Ch Heiden. "Transport properties of niobium-silicon superconductor-semiconductor junctions." Physica B: Condensed Matter 204, no. 1-4 (January 1995): 183–89. http://dx.doi.org/10.1016/0921-4526(94)00261-s.

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17

Guo, Ruyan, A. S. Bhalla, Jyh Sheen, F. W. Ainger, S. Erdei, E. C. Subbarao, and L. E. Cross. "Strontium aluminum tantalum oxide and strontium aluminum niobium oxide as potential substrates for HTSC thin films." Journal of Materials Research 10, no. 1 (January 1995): 18–25. http://dx.doi.org/10.1557/jmr.1995.0018.

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Single crystal fibers of A(B11/2B21/2)O3 perovskites type with compositions Sr(Al1/2Ta1/2)O3 (SAT) and Sr(Al1/2Nb1/2)O3 (SAN) were grown successfully for the first time, using a laser-heated pedestal growth (LHPG) technique. Their crystallographic structures were found to be simple cubic perovskite with lattice parameters a = 3.8952 Å (SAT) and a = 3.8995 Å (SAN) that are close lattice matches to the YBCO superconductors. No structural phase transitions or twins have been found, and the average coefficients of the thermal expansion match well with the YBCO superconductor materials. We report that SAT is one of the most promising substrates to date for the epitaxial growth of HTSC thin films suitable for microwave device applications as it has low dielectric constants (K ∼ 11–12, at 100 Hz–10 GHz and 300 K) and low dielectric loss (∼4 × 10−5 at 10 kHz and 80 K), together with lattice parameter matching, thermal expansion matching, and chemical compatibility with the high Tc superconductors (YBCO).

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18

Тарасов, М. А., А. А. Ломов, А. М. Чекушкин, А. А. Гунбина, М. Ю. Фоминский, C. В. Краевский, Р. К. Козулин, and А. В. Шадрин. "Предельные параметры СИС-переходов в теории и технологические возможности их достижения." Физика твердого тела 65, no. 7 (2023): 1140. http://dx.doi.org/10.21883/ftt.2023.07.55835.29h.

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Tunneling Josephson junctions of the superconductor-insulator-superconductor (SIS) type have a history of more than 50 years, and theoretical estimates of the ultimate parameters of devices for receiving and processing signals based on them look very promising. In practice, in many cases, the actually achieved parameters turn out to be much worse than the theoretical ones, so for niobium SQUIDs the characteristic voltage Vc=IcRn at best reaches 200 µV, and according to theory it should be up to 2 mV. For Terahertz SIS mixers and oscillators, the main problems are a large specific capacitance, hysteresis, and leakage currents. These problems may be related to the morphology and crystal structure of superconductor films. In practice, films are granular, tunnel barriers are nonuniform, the effective area is about 10% of geometric area, leakage currents, parasitic capacitances occur. The crystal structure determines fundamentally different properties of the same elements, for example, for carbon it is diamond, graphite, fullerenes, nanotubes. Important components of a promising superconducting technology are: the use of single-crystal substrates matched in lattice constant and orientation with the grown films, optimization of growth temperature conditions, controlled formation of an oxide or nitride tunnel barrier. One option is to use a Schottky barrier for the semiconductor interlayer instead of a dielectric or normal metal one. This review presents the results of studying films by X-ray diffraction diagnostics, atomic force microscopy, and electron microscopy, showing the main bottlenecks of the existing technology with the deposition of niobium, niobium nitride, and aluminum films on oxidized standard silicon substrates, as well as the results of quasi-epitaxial growth of films on single-crystal substrates at various temperature conditions. Reproducible manufacturing of high-quality tunnel junctions can be achieved by implementing atomically smooth surfaces of tunnel contacts, which will improve the signal and noise characteristics of superconducting devices for receiving and processing information.

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19

Jackson, B. D., G. de Lange, T. Zijlstra, M. Kroug, T. M. Klapwijk, and J. A. Stern. "Niobium titanium nitride-based superconductor-insulator-superconductor mixers for low-noise terahertz receivers." Journal of Applied Physics 97, no. 11 (June 2005): 113904. http://dx.doi.org/10.1063/1.1927281.

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20

Tan, B.-K., K. Rudakov, V. P. Koshelets, A. Khudchenko, A. M. Baryshev, and G. Yassin. "Comparing the performance of 850 GHz integrated bias-tee superconductor-insulator-superconductor (SIS) mixers with single- and parallel-junction tuner." Superconductor Science and Technology 35, no. 12 (November 7, 2022): 125008. http://dx.doi.org/10.1088/1361-6668/ac9d6e.

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Abstract We present and compare the design and performance of two 850 GHz radial probe fed superconductor-insulator-superconductor mixers, where the antenna is aligned perpendicular to the E-Plane of the input full-height rectangular waveguide connected to a multiple flare-angles smooth-walled horn. Both designs are comprised of 0.5 µm2 hybrid niobium/aluminium-nitride/niobium-nitride tunnel junction, fabricated on top of a niobium titanium nitride ground plane with an Al wiring layer. The entire superconducting circuit is supported with a 40 µm thick quartz substrate. The major difference between the two designs is the method used to cancel out the parasitic junction capacitance for broadband performance. The first design utilises two identical junctions connected in parallel with a short transmission line to convert the capacitance of one junction into the equivalent inductance of the other junction, commonly known as the twin-junction tuning scheme; whilst the second design employs an end-loaded scheme with only one tunnel junction. We found that both methods offer similar radio frequency performances, with close to 2× the double sideband quantum noise temperature, but the twin-junction design is more resilient to fabrication tolerances. However, the end-loaded design offers a much better intermediate frequency (IF) bandwidth performance, made possible by the sub-micron and high current density tunnel junction technology. The improved IF performance is important for many millimetre (mm) and sub-mm observatories, such as future upgrades of Atacama Large Millimetre/sub-mm Array receivers, as well as forthcoming space-borne far-infrared missions. Therefore, we conclude that the single-junction mixer design is the preferred option for THz applications, as long as the fabrication error can be minimised within a certain limit.

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21

Miyakawa, Kazuki, Hiroki Takata, Taishi Yamaguchi, Yuji Inagaki, Kazumasa Makise, and Tatsuya Kawae. "Hydrogen-impurity-induced conductance peaks in constriction type Josephson junctions." Applied Physics Express 15, no. 1 (December 24, 2021): 013002. http://dx.doi.org/10.35848/1882-0786/ac42ff.

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Abstract We studied hydrogen (H) and deuterium (D) impurity effects of superconducting Josephson current flowing through the superconductor-constriction-superconductor Josephson junctions (ScS-JJ). When H or D impurities are adsorbed on the surface of the ScS-JJ prepared by niobium or lead, many spike-like peaks with almost the same spacing appear inside the superconducting gap in addition to anomalies owing to the multiple Andreev reflection in the differential conductance spectra. The spacing between the adjacent peaks is independent of the temperature variation. These indicate that H or D impurities adsorbed on the JJ are sources of noise for the Josephson current.

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22

Smolyaninov, Igor I., and Vera N. Smolyaninova. "Metamaterial superconductors." Nanophotonics 7, no. 5 (May 24, 2018): 795–818. http://dx.doi.org/10.1515/nanoph-2017-0115.

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AbstractSearching for natural materials exhibiting larger electron-electron interactions constitutes a traditional approach to high-temperature superconductivity research. Very recently, we pointed out that the newly developed field of electromagnetic metamaterials deals with the somewhat related task of dielectric response engineering on a sub-100-nm scale. Considerable enhancement of the electron-electron interaction may be expected in such metamaterial scenarios as in epsilon near-zero (ENZ) and hyperbolic metamaterials. In both cases, dielectric function may become small and negative in substantial portions of the relevant four-momentum space, leading to enhancement of the electron pairing interaction. This approach has been verified in experiments with aluminum-based metamaterials. Metamaterial superconductor with Tc=3.9 K have been fabricated, which is three times that of pure aluminum (Tc=1.2 K), which opens up new possibilities to improve the Tc of other simple superconductors considerably. Taking advantage of the demonstrated success of this approach, the critical temperature of hypothetical niobium, MgB2- and H2S-based metamaterial superconductors is evaluated. The MgB2-based metamaterial superconductors are projected to reach the liquid nitrogen temperature range. In the case of an H2S-based metamaterial, the projected Tc appears to reach ~250 K.

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23

Željko Đ, Vujović. "Magnets, Gradients, and RF Coils of MR Scanners." International Journal of Physics Research and Applications 6, no. 2 (July 25, 2023): 128–35. http://dx.doi.org/10.29328/journal.ijpra.1001062.

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The topic of this paper is the parts of modern MR devices, which contain magnet coils. MR scanner magnets are made of four types of electromagnetic coils: 1) Main magnet, made of superconducting material. The main magnet of an MR (Magnetic Resonance Imaging) scanner creates a strong and uniform magnetic field around the patient being scanned. This magnetic field is typically in the range of 0.5 to 3 Tesla and is used to align the magnetic moments of the hydrogen atoms in the patient's body. The superconductors, which create the main magnetic field, should be cooled with liquid helium and liquid nitrogen. The main magnets made of superconductors should use a cryostat, with cooling vessels with liquid helium and liquid nitrogen, thermal insulation, and other protective elements of the magnet system. 2) The gradient magnetic field is made of three types of coils: x-coils, y-coils, and z-coils. The X coil, made of resistive material, creates a variable magnetic field, horizontally, from left to right, across the scanning tube; 3) The Y coil creates a variable magnetic field, vertically, from bottom to top; 4) The Z coil creates a variable magnetic field, longitudinally, from head to toe, inside the scanning tube. RF coils are used to generate RF pulses to excite the hydrogen protons (spins) in the patient's body and detect the signals emitted by the protons when they return to their equilibrium state after the RF excitation is turned off. The resulting interaction between the magnetic field and the aligned hydrogen atoms produces a signal that is used to generate the images seen in an MRI scan. The main magnetic field is what allows MR imaging to produce detailed anatomical and functional information non-invasively. The structure of the MR scanner magnet is complex. The resonant frequency changes at each point of the field in a controlled manner. Inside the copper core are embedded the windings of the main magnet made of superconducting material in the form of microfibers. A non-linear gradient field is created by coils of conductive material. It adds to the main magnetic field. Thus the resulting magnetic field is obtained. The types of magnets that exist in the basic configurations of MR scanners are analyzed. Scanners in the form of a closed cylindrical cavity generate their magnetic fields by passing current through a solenoid, which is maintained at the temperature of a superconductor. Exclusively used superconductors are niobium-titanium (NbTi), niobium-tin (Nb3Sn), vanadium-gallium (V3Ga), and magnesium-diboride (MgB2). Only magnesium diboride is a high-temperature superconductor, with a critical temperature Tc = 390K. The three remaining superconductors are low temperatures. New high-temperature superconductors have been discovered, as well as superconductors at room temperature. Newly discovered superconducting materials are not used in MR scanners.

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24

Kayyalha, Morteza, Di Xiao, Ruoxi Zhang, Jaeho Shin, Jue Jiang, Fei Wang, Yi-Fan Zhao, et al. "Absence of evidence for chiral Majorana modes in quantum anomalous Hall-superconductor devices." Science 367, no. 6473 (January 2, 2020): 64–67. http://dx.doi.org/10.1126/science.aax6361.

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A quantum anomalous Hall (QAH) insulator coupled to an s-wave superconductor is predicted to harbor chiral Majorana modes. A recent experiment interprets the half-quantized two-terminal conductance plateau as evidence for these modes in a millimeter-size QAH-niobium hybrid device. However, non-Majorana mechanisms can also generate similar signatures, especially in disordered samples. Here, we studied similar hybrid devices with a well-controlled and transparent interface between the superconductor and the QAH insulator. When the devices are in the QAH state with well-aligned magnetization, the two-terminal conductance is always half-quantized. Our experiment provides a comprehensive understanding of the superconducting proximity effect observed in QAH-superconductor hybrid devices and shows that the half-quantized conductance plateau is unlikely to be induced by chiral Majorana fermions in samples with a highly transparent interface.

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25

Wolter, Silke, Julian Linek, Josepha Altmann, Thomas Weimann, Sylke Bechstein, Reinhold Kleiner, Jörn Beyer, Dieter Koelle, and Oliver Kieler. "Fabrication Process for Deep Submicron SQUID Circuits with Three Independent Niobium Layers." Micromachines 12, no. 4 (March 24, 2021): 350. http://dx.doi.org/10.3390/mi12040350.

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We present a fabrication technology for nanoscale superconducting quantum interference devices (SQUIDs) with overdamped superconductor-normal metal-superconductor (SNS) trilayer Nb/HfTi/Nb Josephson junctions. A combination of electron-beam lithography with chemical-mechanical polishing and magnetron sputtering on thermally oxidized Si wafers is used to produce direct current SQUIDs with 100-nm-lateral dimensions for Nb lines and junctions. We extended the process from originally two to three independent Nb layers. This extension offers the possibility to realize superconducting vias to all Nb layers without the HfTi barrier, and hence to increase the density and complexity of circuit structures. We present results on the yield of this process and measurements of SQUID characteristics.

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26

Baskaran, R., A. V. Thanikai Arasu, E. P. Amaladass, and M. P. Janawadkar. "High upper critical field in disordered niobium nitride superconductor." Journal of Applied Physics 116, no. 16 (October 28, 2014): 163908. http://dx.doi.org/10.1063/1.4900436.

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27

Mishra, P. K., G. Ravikumar, V. C. Sahni, M. R. Koblischka, and A. K. Grover. "Surface pinning in niobium and a high-Tc superconductor." Physica C: Superconductivity 269, no. 1-2 (September 1996): 71–75. http://dx.doi.org/10.1016/0921-4534(96)00462-5.

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28

A.M. Chekushkin, L.V. Filippenko, A.A. Lomov, Liu Dong, Shi Sheng-Cai, and V.P. Koshelets. "Optimization of fabrication processes for Nb, NbN, NbTiN films and high-quality tunnel junctions for terahertz receiving circuits." Technical Physics 92, no. 13 (2022): 2136. http://dx.doi.org/10.21883/tp.2022.13.52234.135-21.

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This paper describes the optimization of the existing technology for the fabrication of superconducting films and high-quality tunnel junctions on a magnetron sputtering facility. To expand the frequency range to 1.1 THz and to obtain the limiting parameters of superconducting elements, the regimes of production of Nb, NbN, NbTiN films were optimized. These films are used to fabricate superconductor-insulator-superconductor Nb/Al--AlN/NbN tunnel junctions. Al and NbTiN films are required to create receiving elements at frequencies above 700 GHz (the cutoff frequency for niobium); such structures are being developed for the radio astronomy array receiver located in the Atacama Pathfinder Experiment telescope. Keywords: superconductivity, tunnel junctions, magnetron sputtering, thin films.

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29

Wang, Mei-Xiao, Canhua Liu, Jin-Peng Xu, Fang Yang, Lin Miao, Meng-Yu Yao, C. L. Gao, et al. "The Coexistence of Superconductivity and Topological Order in the Bi2Se3 Thin Films." Science 336, no. 6077 (March 15, 2012): 52–55. http://dx.doi.org/10.1126/science.1216466.

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Three-dimensional topological insulators (TIs) are characterized by their nontrivial surface states, in which electrons have their spin locked at a right angle to their momentum under the protection of time-reversal symmetry. The topologically ordered phase in TIs does not break any symmetry. The interplay between topological order and symmetry breaking, such as that observed in superconductivity, can lead to new quantum phenomena and devices. We fabricated a superconducting TI/superconductor heterostructure by growing dibismuth triselenide (Bi2Se3) thin films on superconductor niobium diselenide substrate. Using scanning tunneling microscopy and angle-resolved photoemission spectroscopy, we observed the superconducting gap at the Bi2Se3 surface in the regime of Bi2Se3 film thickness where topological surface states form. This observation lays the groundwork for experimentally realizing Majorana fermions in condensed matter physics.

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Barber, Z. H., and M. G. Blamire. "Niobium nitride/aluminium nitride superconductor/insulator multilayers and tunnel junctions." IEEE Transactions on Appiled Superconductivity 7, no. 2 (June 1997): 3609–12. http://dx.doi.org/10.1109/77.622186.

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Venkateshwarlu, D., V. Ganesan, Y. Ohashi, S. Kikkawa, and J. V. Yakhmi. "Fluctuation effects in the niobium oxynitride (Nb0.87Si0.09□0.04)(N0.87O0.13) superconductor." Superconductor Science and Technology 27, no. 8 (June 19, 2014): 085002. http://dx.doi.org/10.1088/0953-2048/27/8/085002.

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Chaudhuri, S., M. R. Nevala, and I. J. Maasilta. "Niobium nitride-based normal metal-insulator-superconductor tunnel junction microthermometer." Applied Physics Letters 102, no. 13 (April 2013): 132601. http://dx.doi.org/10.1063/1.4800440.

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Febvre, Pascal, David Bouis, Natascia De Leo, Matteo Fretto, Andrea Sosso, and Vincenzo Lacquaniti. "Electrical parameters of niobium-based overdamped superconductor-normal metal-insulator-superconductor Josephson junctions for digital applications." Journal of Applied Physics 107, no. 10 (May 15, 2010): 103927. http://dx.doi.org/10.1063/1.3354090.

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Talantsev, Evgeny F. "Quantifying the Nonadiabaticity Strength Constant in Recently Discovered Highly Compressed Superconductors." Symmetry 15, no. 9 (August 24, 2023): 1632. http://dx.doi.org/10.3390/sym15091632.

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Superconductivity in highly pressurized hydrides has become the primary direction for the exploration of the fundamental upper limit of the superconducting transition temperature, Tc, after Drozdov et al. (Nature 2015, 525, 73) discovered a superconducting state with Tc=203 K in highly compressed sulfur hydride. To date, several dozen high-temperature superconducting polyhydrides have been discovered and, in addition, it was recently reported that highly compressed titanium and scandium exhibit record-high Tc (up to 36 K). This exceeded the Tc=9.2 K value of niobium many times over, which was the record-high Tc ambient pressure metallic superconductor. Here, we analyzed the experimental data for the recently discovered high-pressure superconductors (which exhibit high transition temperatures within their classes): elemental titanium (Zhang et al., Nature Communications 2022; Liu et al., Phys. Rev. B 2022), TaH3 (He et al., Chinese Phys. Lett. 2023), LaBeH8 (Song et al., Phys. Rev. Lett. 2023), black phosphorous (Li et al., Proc. Natl. Acad. Sci. 2018; Jin et al., arXiv 2023), and violet (Wu et al., arXiv 2023) phosphorous to reveal the nonadiabaticity strength constant TθTF (where Tθ is the Debye temperature, and TF the Fermi temperature) in these superconductors. The analysis showed that the δ-phase of titanium and black phosphorous exhibits TθTF scores that are nearly identical to those associated with A15 superconductors, while the studied hydrides and violet phosphorous exhibit constants in the same ballpark as those of H3S and LaH10.

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Dhal, Jyoti Prakash, and Subash Chandra Mishra. "Effect of Niobium/Molybdenum Microalloying on SS316LN Steel." Applied Mechanics and Materials 110-116 (October 2011): 1259–63. http://dx.doi.org/10.4028/www.scientific.net/amm.110-116.1259.

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In recent years SS316LN microalloyed stainless steel is preferred for use as jacket material for Nb3Sn superconductor strands/wires. In the present investigation, microalloyed SS316LN is prepared in a vacuum induction melting furnace; Niobium and Molybdenum in their ferroalloy stage are considered as alloying element. This microalloyed steels are cast in water cooled copper mould. The tensile strength and elongation are measured and the fracture surface is studied under scanning electron microscope. It is observed that, there is a reduction of tensile strength and decrease in hardness of the steels prepared with addition of either/both the alloying elements; however there is an increase in ductility, which is helpful for cold rolling operation. From the micrographs it is observed that nitride precipitates are formed along the grain boundary, but formation of chromium carbide precipitates is reduced.

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Tateishi, H., K. Agatsuma, K. Arai, M. Umeda, K. Gotoh, N. Sadakata, and T. Saitoh. "Properties of fiber-reinforced niobium-tin superconductor fabricated by bronze process." IEEE Transactions on Appiled Superconductivity 9, no. 2 (June 1999): 1437–40. http://dx.doi.org/10.1109/77.784653.

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Kondoh, J., H. Tateishi, M. Umeda, K. Arai, K. Agatsuma, K. Gotoh, and T. Saitoh. "Mechanical properties of a niobium-tin superconductor reinforced by tantalum cores." IEEE Transactions on Appiled Superconductivity 11, no. 1 (March 2001): 3635–38. http://dx.doi.org/10.1109/77.919852.

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Dinner, Rafael B., Suman-Lata Sahonta, Rong Yu, Nadia A. Stelmashenko, Judith L. MacManus-Driscoll, and Mark G. Blamire. "Superconductor–ferromagnet nanocomposites created by co-deposition of niobium and dysprosium." Superconductor Science and Technology 22, no. 7 (June 2, 2009): 075001. http://dx.doi.org/10.1088/0953-2048/22/7/075001.

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Xu, Bu‐xin, and W. O. Hamilton. "Combined mu‐metal and niobium superconductor shielding for dc SQUID operation." Review of Scientific Instruments 58, no. 2 (February 1987): 311–12. http://dx.doi.org/10.1063/1.1139278.

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Zhu, Zhen, Michał Papaj, Xiao-Ang Nie, Hao-Ke Xu, Yi-Sheng Gu, Xu Yang, Dandan Guan, et al. "Discovery of segmented Fermi surface induced by Cooper pair momentum." Science 374, no. 6573 (December 10, 2021): 1381–85. http://dx.doi.org/10.1126/science.abf1077.

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Imaging a peculiar Fermi surface Running a current through a superconductor can cause the superconducting gap to close on a section of the Fermi surface. However, observing this segmented Fermi surface directly is tricky. To do so, Zhu et al . worked with a thin film of the topological insulator bismuth telluride placed on top of superconducting niobium diselenide. A small applied magnetic field caused a screening current, which in turn led to a segmented Fermi surface in the topological insulator layer. Using a scanning tunneling microscope, the researchers were able to map out this Fermi surface. —JS

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Vasyutin M. A., Kuz’michev N. D., and Shilkin D.A. "Experimental method for controlling the overheating of superconducting films under the action of a pulsed current." Technical Physics Letters 48, no. 7 (2022): 73. http://dx.doi.org/10.21883/tpl.2022.07.54045.19131.

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Using time sweeps of the current through a sample of a superconducting film, the effect of the current sweep rate on the process of heat propagation from current contacts is investigated. The samples used were NbN films with temperatures below and above the temperature of transition to the superconducting state. A method for determining the critical heating of key zones of the sample is proposed. The propagation velocities of the resistive front and normal domain in a superconductor are estimated at different temperatures. Keywords: niobium nitride films, time sweep of the current, resistive front, normal domain.

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Togawa, Yoshihiko, Ken Harada, Tetsuya Akashi, Hiroto Kasai, Tsuyoshi Matsuda, Atsutaka Maeda, and Akira Tonomura. "Rectified motion of vortices in a niobium superconductor observed by Lorentz microscopy." Physica C: Superconductivity 426-431 (October 2005): 141–46. http://dx.doi.org/10.1016/j.physc.2005.04.029.

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43

Semchinova, O. K., I. V. Grekchov, L. A. Delimova, and I. A. Linijchuck. "Niobium induced metal-superconductor to metal-insulator transition in the YBCO system." IEEE Transactions on Appiled Superconductivity 5, no. 2 (June 1995): 1459–62. http://dx.doi.org/10.1109/77.402841.

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Vakhrushev, A. V., A. Yu Fedotov, Yu B. Savva, and A. S. Sidorenko. "Modeling the processes of atom structure formation of a superconducting spin valve." PNRPU Mechanics Bulletin, no. 2 (December 15, 2020): 16–27. http://dx.doi.org/10.15593/perm.mech/2020.2.02.

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The paper considers the modeling of a multilayer nanocomposite, the combination of elements of which gives rise to a spin valve effect. The relevance and importance of effects in the field of spintronics and related materials and devices are described. We study the composition and atomic structure of individual layers of a multilayer nanocomposite, as well as the composition and morphology of the interface of nanocomposite layers. We analyzed a sample with a periodic superconductor-ferromagnet structure consisting of more than 20 alternating layers of niobium and cobalt. The deposition process took place in a deep vacuum. The simulation was carried out by the molecular dynamics method using the potential of the modified immersed atom method. The formation of layers was carried out in a stationary mode. The temperature was adjusted using the Nose-Hoover thermostat. The deposition of each nanofilm ended with a relaxation stage for the necessary stabilization and restructuring of the formed nanocomposite. Three deposition temperature regimes were considered: 300 K, 500 K, and 800 K. For these modes, we analysed the atomic structure of nanofilms and transition regions (interface) formed between the layers. A study of the atomic structure of nanofilms showed that niobium is formed by crystalline regions of different orientations. A cobalt nanofilm is characterized by a structure close to amorphous. The structural features of the interface between the superconductor-ferromagnet layers largely depend on a relief of the surface onto which the deposition is made. The smallest variation in atomic composition is observed in the first niobium-cobalt contact zone, since the formation of the first nanofilm occurs on an even plane of the substrate. An analysis of the influence of the temperature regime during the formation of the nanosystem shows the dependence of the processes of formation of multilayer nanofilm formation, the interface of nanolayers, as well as the composition and morphology of heterostructures on the temperature at which a nanocomposite is manufactured. An increased temperature leads to the formation of a more rarefied structure of nanolayers and an increase in the zones of the interface of nanolayers due to the diffusion of atoms of the sprayed materials.

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Seko, Kazuyuki, Yoshiko Ichikawa, Ryo Terajima, Joe Sakai, and Syozo Imai. "Fabrication of niobium superconductor–insulator–superconductor junctions with a magnetic tunneling barrier NiOx for millimeter and submillimeter mixer applications." Journal of Applied Physics 92, no. 5 (September 2002): 2810–15. http://dx.doi.org/10.1063/1.1500415.

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46

Garcia Borges, Dalton, Márcia Regina Baldissera, Geovani Rodrigues, Mírian de Lourdes Noronha Motta Melo, Rayana Fernanda Ribeiro Lourenço, and Gilbert Silva. "Microstructural and Mechanical Characterization of the Niobium Cold Deformed-Swage." Materials Science Forum 805 (September 2014): 362–67. http://dx.doi.org/10.4028/www.scientific.net/msf.805.362.

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The refractory metals and their alloys show excellent mechanical behavior in high temperatures and high resistance to corrosion and to wear and good thermal conductivity. The metals that constitute this group are, traditionally, tantalum, molybdenum, tungsten and niobium. Niobium (Nb) is a metal with 2468°C melting point, density 8.57 g/cm3 and CCC crystalline structure, is characterized by its excellent ductility and reasonable mechanical resistance in high temperatures. Due to these properties, o Nb is applied in chemical, nuclear and electrical industry and in the superconductor wire production. One of the processes used in niobium plastic deformation is the swage that consists in one direct deformation process, which can be done at hot or cold temperature, used to modify the transversal section area of bars, tubes and wires. The microstructure evolution during a plastic deformation is very important in the relation of deformation mechanism, mechanical property and texture formation. The aim of this work is to evaluate the microstructural and mechanical behavior of metal cold rotary forging – swage using the techniques of Scanning Electronic Microscopic – SEM e microhardeness Vickers. Metallographic analysis of the microstructure of Nb after deformation of 96.4%, shows a distorted shape called "ripple". The Vickers microhardeness results indicate that there is a gradual increase in the microhardness of Nb up to 80% reduction in area taking place stabilization after this value. It may be noted that in both directions, the center of sample had higher hardness values

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He, Y., C. Muirhead, A. Bradshaw, J. Abell, C. Schank, G. Geibel, and F. Steglich. "Coherence of the superconducting wavefunction between the heavy-fermion superconductor UPd2AI3 and niobium." Nature 357, no. 6375 (May 1992): 227–29. http://dx.doi.org/10.1038/357227a0.

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48

Gupta, Vaibhav, John A. Sellers, Charles D. Ellis, Bhargav Yelamanchili, Simin Zou, Yang Cao, David B. Tuckerman, and Michael C. Hamilton. "Minimizing Film Stress and Degradation in Thin-Film Niobium Superconducting Cables." Additional Conferences (Device Packaging, HiTEC, HiTEN, and CICMT) 2017, DPC (January 1, 2017): 1–25. http://dx.doi.org/10.4071/2017dpc-tha3_presentation4.

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The future of superconducting and cryogenic electronic systems can significantly benefit from densely integrated superconducting multi-layer and multi-signal flexible cables due to the massive number of electrical interconnects needed in systems such as superconducting quantum computers and cryogenic detector arrays. In order to maintain superconductivity in niobium (Nb) thin films, film stress and degradation must be minimized. We are working towards configurations with embedded traces, where it is expected that the superconductor material will be subjected to subsequent fabrication steps that must not degrade the properties of the superconductor. We previously observed degradation of the superconducting properties of Nb, such as reduction of both transition temperature and critical current, as a result of curing a polyimide passivation layer at supplier recommended curing temperature (350 oC). The deterioration in the superconducting properties may be due to mechanical stress in the film or diffusion of impurities into the Nb during the curing process Film stress plays a vital role in the superconducting properties of Nb. Previous research by other groups has focused on in situ ion bombardment, substrate fixturing and wafer preparation in order to minimize film stress. In this work, we discuss the role of argon (Ar) pressure and power during Nb sputtering on the quality of Nb and Nb/Al thin films. By varying the Ar pressure and applied power during sputter deposition, we have produced both tensile and compressive films on flexible substrates in order to find the pressure that yields a near zero stress Nb and Nb/Al thin film at room temperature. A low stress Nb film was tested with a thin Al barrier layer (of the order of 10's of nm) between Nb and polyimide to protect the Nb superconductivity during the PI curing step. Nb traces with a thickness of roughly 250nm and a width of 50um were used for this work. Nb films deposited at different Ar pressures and power levels were tested for critical transition temperature (Tc), critical current (Ic), and sheet resistance (Ω/□), to compare the superconducting behavior of different Nb films. Details of the fabrication processes, experimental procedures and performance results will be presented. This work will help determine materials stacks-ups that may be useful for future multi-layer Nb-based flexible superconducting cables. Acknowledgment: We gratefully acknowledge financial support and technical guidance from Microsoft Research for this work.

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Chen, Sheng-Zong, Jing-Wei Yang, Tzu-Yu Peng, Yu-Cheng Chu, Ching-Chen Yeh, I.-Fan Hu, Swapnil Mhatre, Yu-Jung Lu, and Chi-Te Liang. "Disorder-induced 2D superconductivity in a NbTiN film grown on Si by ultrahigh-vacuum magneton sputtering." Superconductor Science and Technology 35, no. 6 (April 21, 2022): 064003. http://dx.doi.org/10.1088/1361-6668/ac6631.

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Abstract We report on the growth and characterization of a niobium titanium nitride (NbTiN) film on a Si substrate prepared by ultrahigh vacuum sputtering. We show that the superconducting transition temperature is lower than those of high-quality NbTiN films. Interestingly, even though the zero-temperature Ginzburg-Landau coherence length (=9.77 nm) is significantly shorter than the film thickness (=86 nm), we are still able to observe the Berezinskii-Kosterlitz-Thouless-like transition, indicating the two-dimensional (2D) signature of our three-dimensional (3D) sample. We propose that the mechanism of hidden 2D superconducting property is similar to the recently reported results of the disordered induced 3D to 2D superconductor transition. We suggest further theoretical work is required for studying our new experimental results.

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Jäck, Berthold, Yonglong Xie, Jian Li, Sangjun Jeon, B. Andrei Bernevig, and Ali Yazdani. "Observation of a Majorana zero mode in a topologically protected edge channel." Science 364, no. 6447 (June 13, 2019): 1255–59. http://dx.doi.org/10.1126/science.aax1444.

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Superconducting proximity pairing in helical edge modes, such as those of topological insulators, is predicted to provide a unique platform for realizing Majorana zero modes (MZMs). We used scanning tunneling microscopy measurements to probe the influence of proximity-induced superconductivity and magnetism on the helical hinge states of bismuth(111) films grown on a superconducting niobium substrate and decorated with magnetic iron clusters. Consistent with model calculations, our measurements revealed the emergence of a localized MZM at the interface between the superconducting helical edge channel and the iron clusters, with a strong magnetization component along the edge. Our experiments also resolve the MZM’s spin signature, which distinguishes it from trivial in-gap states that may accidentally occur at zero energy in a superconductor.

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