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Träfflista för sökning "WFRF:(Bauch Thilo 1972) ;pers:(Baghdadi Reza 1984)"

Sökning: WFRF:(Bauch Thilo 1972) > Baghdadi Reza 1984

  • Resultat 1-10 av 11
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1.
  • Charpentier, Sophie, 1983, et al. (författare)
  • Hot spot formation in electron-doped PCCO nanobridges
  • 2016
  • Ingår i: Physical Review B. - 2469-9969 .- 2469-9950. ; 94:6
  • Tidskriftsartikel (refereegranskat)abstract
    • We have investigated the transport properties of optimally doped Pr2-xCexCuO4-δ (PCCO) nanobridges with width down to 100 nm. The critical current density of the nanobridges approaches the Ginzburg-Landau theoretical limit, which demonstrates nanostructures with properties close to the as-grown films. The current voltage characteristics are hysteretic with a sharp voltage switch, of the order of a few millivolts, that we interpret with the occurrence of a hot spot formation. The values of the retrapping current and the voltage switch obtained by modeling the heat transport in the nanobridges are very close to the experimental ones. This feature, together with the extremely short recombination times, make PCCO nanostructures attractive candidates for ultrafast single photon detectors.
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2.
  • Arpaia, Riccardo, 1985, et al. (författare)
  • Improved noise performance of ultrathin YBCO Dayem bridge nanoSQUIDs
  • 2017
  • Ingår i: Superconductor Science and Technology. - : IOP Publishing. - 0953-2048 .- 1361-6668. ; 30:1
  • Tidskriftsartikel (refereegranskat)abstract
    • We have fabricated YBa2Cu3O7-delta (YBCO) nano superconducting quantum interference devices (nanoSQUIDs), realized in Dayem bridge configuration, on films with thickness down to 10 nm. The devices, which have not been protected by a Au capping layer during the nanopatterning, show modulations of the critical current as a function of the externally applied magnetic field from 300 mK up to the critical temperature of the nanobridges. The absence of the Au shunting layer and the enhancement of the sheet resistance in ultrathin films lead to very large voltage modulations and transfer functions, which make these nanoSQUIDs highly sensitive devices. Indeed, by using bare YBCO nanostructures, we have revealed an upper limit for the intrinsic white flux noise level S-Phi,w(1/2)
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3.
  • Arpaia, Riccardo, 1985, et al. (författare)
  • Resistive state triggered by vortex entry in YBa2Cu3O7-delta nanostructures
  • 2014
  • Ingår i: Physica C: Superconductivity and its Applications. - : Elsevier BV. - 0921-4534. ; 506, s. 165-168
  • Tidskriftsartikel (refereegranskat)abstract
    • We have realized YBa2Cu3O7-delta nanowires and nano Superconducting Quantum Interference Devices (nanoSQUID). The measured temperature dependence of the wire resistances below the superconducting transition temperature has been analyzed using a thermally activated vortex entry model valid for wires wider than the superconducting coherence length. The extracted zero temperature values of the London penetration depth, lambda(0) similar or equal to 270 +/- 15 nm, are in good agreement with the value obtained from critical current modulations as a function of an externally applied magnetic field in a nanoSQUID implementing two nanowires.
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4.
  • Arpaia, Riccardo, 1985, et al. (författare)
  • Transport properties of ultrathin YBa2Cu3O7-delta nanowires: A route to single-photon detection
  • 2017
  • Ingår i: Physical Review B. - 2469-9969 .- 2469-9950. ; 96:6
  • Tidskriftsartikel (refereegranskat)abstract
    • We report on the growth and characterization of ultrathin YBa2Cu3O7-delta (YBCO) films on MgO (110) substrates, which exhibit superconducting properties at thicknesses down to 3 nm. YBCO nanowires, with thicknesses down to 10 nm and widths down to 65 nm, have also been successfully fabricated. The nanowires protected by a Au capping layer showsuperconducting properties close to the as-grown films and critical current densities, which are limited by only vortex dynamics. The 10-nm-thick YBCO nanowires without the Au capping present hysteretic current-voltage characteristics, characterized by a voltage switch which drives the nanowires directly from the superconducting to the normal state. We associate such bistability to the presence of localized normal domains within the superconductor. The presence of the voltage switch in ultrathin YBCO nanostructures, characterized by high sheet resistance values and high critical current values, makes our nanowires very attractive devices to engineer single-photon detectors.
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5.
  • Arzeo, Marco, 1986, et al. (författare)
  • Toward ultra high magnetic field sensitivity YBa2Cu3O7 - δ nanowire based superconducting quantum interference devices
  • 2016
  • Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 119:17
  • Tidskriftsartikel (refereegranskat)abstract
    • We report on measurements of YBa2Cu3O7- ? nanowire based Superconducting QUantum Interference Devices (nanoSQUIDs) directly coupled to an in-plane pick-up loop. The pick-up loop, which is coupled predominantly via kinetic inductance to the SQUID loop, allows for a significant increase of the effective area of our devices. Its role is systematically investigated and the increase in the effective area is successfully compared with numerical simulations. Large effective areas, together with the ultra low white flux noise below 1 ? ? 0 / Hz, make our nanoSQUIDs very attractive as magnetic field sensors.
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6.
  • Baghdadi, Reza, 1984, et al. (författare)
  • Fabricating Nanogaps in YBa2Cu3O7-delta for Hybrid Proximity-Based Josephson Junctions
  • 2015
  • Ingår i: Physical Review Applied. - 2331-7019. ; 4:1
  • Tidskriftsartikel (refereegranskat)abstract
    • The advances of nanotechnologies applied to high-critical-temperature superconductors (HTSs) have recently given a huge boost to the field, opening new prospectives for their integration in hybrid devices. The feasibility of this research goes through the realization of HTS nanogaps with superconductive properties close to the as-grown bulk material at the nanoscale. Here we present a fabrication approach allowing the realization of YBa2Cu3O7-delta (YBCO) nanogaps with dimensions as small as 35 nm. To assess the quality of the nanogaps, we measure, before and after an ozone treatment, the current-voltage characteristics and the resistance versus temperature of YBCO nanowires with various widths and lengths, fabricated by using different lithographic processes. The analysis of the superconducting transition with a thermally activated vortex-entry model allows us to determine the maximum damage the nanowires undergo during the patterning which relates to the upper bound for the dimension of the nanogap. We find that the effective width of the nanogap is of the order of 100 nm at the superconducting transition temperature while retaining the geometrical value of about 35 nm at lower temperatures. The feasibility of the nanogaps for hybrid Josephson devices is demonstrated by bridging them with thin Au films. We detect a Josephson coupling up to 85 K with an almost ideal magnetic-field response of the Josephson current. These results pave the way for the realization of complex hybrid devices, where tiny HTS nanogaps can be instrumental to study the Josephson effect through barriers such as topological insulators or graphene.
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7.
  • Baghdadi, Reza, 1984, et al. (författare)
  • Josephson effect through YBa2Cu3 O7-δ /Au-encapsulated nanogaps
  • 2017
  • Ingår i: Physical Review B. - 2469-9969 .- 2469-9950. ; 95:17
  • Tidskriftsartikel (refereegranskat)abstract
    • We successfully fabricated and studied planar superconductor-normal-superconductor (SNS) Josephson junctions made of YBa2Cu3O7-? (YBCO) high-TC superconductor (S) and Au normal metal (N). The crucial step in fabrication was done by using a Pt/Au bilayer encapsulation of the patterned YBCO nanogap. This procedure preserves the YBCO nanogap from the degradation due to the contact with resists, water, and chemicals involved in further processing for hybrid devices. The junctions exhibit Fraunhofer-like modulation patterns and Shapiro steps when they are irradiated by a rf field. Furthermore, we analyzed the IC(T) characteristics of our hybrid junctions employing a SINI?S (superconductor-insulator-normal conductor-insulator-superconductor) model.
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8.
  • Baghdadi, Reza, 1984, et al. (författare)
  • Study of in-plane electrical transport anisotropy of alpha-axis oriented YBa2Cu3O7-delta nanodevices
  • 2017
  • Ingår i: Physical Review B. - 2469-9969 .- 2469-9950. ; 95:18, s. Article no. 184505-
  • Tidskriftsartikel (refereegranskat)abstract
    • In the present work, we report the growth of fully untwinned high-quality a-axis-oriented YBa2Cu3O7-delta films on (100) SrLaGaO4 substrates by using PrBa2Cu3O7-delta as a buffer layer. We also fabricated nanowires at different angles gamma with respect to the [0,1,0] direction of the substrate and studied the in-plane anisotropy of the critical current density, which we explained by considering the anisotropy in the coherence length xi and London penetration depth lambda L. Finally, half-integer Shapiro-like steps measured in slightly underdoped c-axis oriented (gamma = 90 degrees) nanowires point towards a different transport regime, which could shed light on intriguing issues of high-critical-temperature superconductors.
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9.
  • Baghdadi, Reza, 1984, et al. (författare)
  • Toward YBa2Cu3O7-δ nanoscale structures for hybrid devices
  • 2015
  • Ingår i: IEEE Transactions on Applied Superconductivity. - 1558-2515 .- 1051-8223. ; 25:3
  • Tidskriftsartikel (refereegranskat)abstract
    • An ex situ ozone annealing has been applied both on YBa2Cu3O7-d (YBCO) films and nanowires. From the investigation on bare films, by measuring the superconducting resistive transition in temperature and the X-ray diffraction pattern, we have observed that the ozonation can be a powerful tool to oxygenate the YBCO structure. To probe the effective role of this reactive annealing on nanostructures, we have fabricated nanowires with widths down to 100 nm, covered by a 20-nm-thick Au layer. We have compared the critical current density and the broadening of the resistance transition measured before and after the ozone treatment, concluding that the ozone is instrumental in recovering very high quality superconducting properties inside the nanostructures, which were degraded by the oxygen out-diffusion occurring during the nanopatterning.
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10.
  • Charpentier, Sophie, 1983, et al. (författare)
  • Induced unconventional superconductivity on the surface states of Bi2Te3 topological insulator
  • 2017
  • Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723 .- 2041-1723. ; 8:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Topological superconductivity is central to a variety of novel phenomena involving the interplay between topologically ordered phases and broken-symmetry states. The key ingredient is an unconventional order parameter, with an orbital component containing a chiral p(x) + ip(y) wave term. Here we present phase-sensitive measurements, based on the quantum interference in nanoscale Josephson junctions, realized by using Bi2Te3 topological insulator. We demonstrate that the induced superconductivity is unconventional and consistent with a sign-changing order parameter, such as a chiral px + ipy component. The magnetic field pattern of the junctions shows a dip at zero externally applied magnetic field, which is an incontrovertible signature of the simultaneous existence of 0 and pi coupling within the junction, inherent to a non trivial order parameter phase. The nano-textured morphology of the Bi2Te3 flakes, and the dramatic role played by thermal strain are the surprising key factors for the display of an unconventional induced order parameter.
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