| 1. |
- Arpaia, Riccardo, 1985, et al.
(författare)
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Transport properties of ultrathin YBa2Cu3O7-delta nanowires: A route to single-photon detection
- 2017
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Ingår i: Physical Review B. - 2469-9969 .- 2469-9950. ; 96:6
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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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| 2. |
- Baghdadi, Reza, 1984, et al.
(författare)
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Study of in-plane electrical transport anisotropy of alpha-axis oriented YBa2Cu3O7-delta nanodevices
- 2017
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Ingår i: Physical Review B. - 2469-9969 .- 2469-9950. ; 95:18, s. Article no. 184505-
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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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| 3. |
- He, Hans, 1989, et al.
(författare)
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Uniform doping of graphene close to the Dirac point by polymer-assisted assembly of molecular dopants
- 2018
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723 .- 2041-1723. ; 9:1
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Tidskriftsartikel (refereegranskat)abstract
- Tuning the charge carrier density of two-dimensional (2D) materials by incorporating dopants into the crystal lattice is a challenging task. An attractive alternative is the surface transfer doping by adsorption of molecules on 2D crystals, which can lead to ordered molecular arrays. However, such systems, demonstrated in ultra-high vacuum conditions (UHV), are often unstable in ambient conditions. Here we show that air-stable doping of epitaxial graphene on SiC—achieved by spin-coating deposition of 2,3,5,6-tetrafluoro-tetracyano-quino-dimethane (F4TCNQ) incorporated in poly(methyl-methacrylate)—proceeds via the spontaneous accumulation of dopants at the graphene-polymer interface and by the formation of a charge-transfer complex that yields low-disorder, charge-neutral, large-area graphene with carrier mobilities ~70 000 cm2V−1s−1at cryogenic temperatures. The assembly of dopants on 2D materials assisted by a polymer matrix, demonstrated by spin-coating wafer-scale substrates in ambient conditions, opens up a scalable technological route toward expanding the functionality of 2D materials.
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| 4. |
- Kunakova, Gunta, 1987, et al.
(författare)
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Topological insulator nanoribbon Josephson junctions: Evidence for size effects in transport properties
- 2020
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 128:19
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Tidskriftsartikel (refereegranskat)abstract
- We have used Bi 2 Se 3 nanoribbons, grown by catalyst-free physical vapor deposition to fabricate high quality Josephson junctions with Al superconducting electrodes. In our devices, we observe a pronounced reduction of the Josephson critical current density J c by reducing the width of the junction, which in our case corresponds to the width of the nanoribbon. Because the topological surface states extend over the entire circumference of the nanoribbon, the superconducting transport associated with them is carried by modes on both the top and bottom surfaces of the nanoribbon. We show that the J c reduction as a function of the nanoribbon width can be accounted for by assuming that only the modes traveling on the top surface contribute to the Josephson transport as we derive by geometrical consideration. This finding is of great relevance for topological quantum circuitry schemes since it indicates that the Josephson current is mainly carried by the topological surface states.
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| 5. |
- Massarotti, D., et al.
(författare)
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What happens in Josephson junctions at high critical current densities
- 2017
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Ingår i: Fizika Nizkih Temperatur. - : AIP Publishing. - 1816-0328 .- 0132-6414. ; 43:7, s. 816-823
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Tidskriftsartikel (refereegranskat)abstract
- The impressive advances in material science and nanotechnology are more and more promoting the use of exotic barriers and/or superconductors, thus paving the way to new families of Josephson junctions. Semiconducting, ferromagnetic, topological insulator and graphene barriers are leading to unconventional and anomalous aspects of the Josephson coupling, which might be useful to respond to some issues on key problems of solid state physics. However, the complexity of the layout and of the competing physical processes occurring in the junctions is posing novel questions on the interpretation of their phenomenology. We classify some significant behaviors of hybrid and unconventional junctions in terms of their first imprinting, i.e. current-voltage curves, and propose a phenomenological approach to describe some features of junctions characterized by relatively high critical current densities Jc. Accurate arguments on the distribution of switching currents will provide quantitative criteria to understand physical processes occurring in high-Jc junctions. These notions are universal and apply to all kinds of junctions. PACS: 74.72.-h Cuprate superconductors; 85.25.Cp Josephson devices; 74.50.+r Tunneling phenomena; Josephson effects.
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| 6. |
- Montemurro, Domenico, 1982, et al.
(författare)
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Enhanced Josephson coupling in hybrid nanojunctions
- 2023
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Ingår i: Physical Review B. - 2469-9969 .- 2469-9950. ; 107:9
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Tidskriftsartikel (refereegranskat)abstract
- We have fabricated NbN/Au nanogaps and bridged them with an Al superconductor using Ti as an interlayer. The nanodevices show a critical current density at 300 mK as high as 3×106A/cm2, which is 30% higher than that of Al nanowires with the same lateral dimensions as the NbN-based devices. The response of the critical current as a function of the external magnetic field clearly showed a Fraunhofer-like behavior, indicating a Josephson coupling between the NbN electrodes through the Al barrier. The superconducting transport evolves into different transport regimes as a function of the temperature. These findings demonstrate the importance of using superconducting barriers in hybrid nanodevices to achieve very high Josephson current in nanodevices of great relevance in superconducting circuits requiring high integration density.
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| 7. |
- Pullukattuthara Surendran, Ananthu, 1994, et al.
(författare)
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Current-phase relation of a short multi-mode Bi 2 Se 3 topological insulator nanoribbon Josephson junction with ballistic transport modes
- 2023
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Ingår i: Superconductor Science and Technology. - 0953-2048 .- 1361-6668. ; 36:6
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Tidskriftsartikel (refereegranskat)abstract
- We used the asymmetric superconducting quantum interference device (SQUID) technique to extract the current phase relation (CPR) of a Josephson junction with a 3D-topological insulator (3D-TI) Bi2Se3 nanobelt as the barrier. The obtained CPR shows deviations from the standard sinusoidal CPR with a pronounced forward skewness. At temperatures below 200 mK, the junction skewness values are above the zero temperature limit for short diffusive junctions. Fitting of the extracted CPR shows that most of the supercurrent is carried by ballistic topological surface states (TSSs), with a small contribution of diffusive channels primarily due to the bulk. These findings are instrumental in engineering devices that can fully exploit the properties of the topologically protected surface states of 3D TIs.
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| 8. |
- Trabaldo, Edoardo, 1990, et al.
(författare)
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Properties of grooved Dayem bridge based YBa2Cu3 O 7 - δ superconducting quantum interference devices and magnetometers
- 2020
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 116:13
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Tidskriftsartikel (refereegranskat)abstract
- The transport properties of a YBa2Cu3 O 7 - δ superconducting quantum interference device (SQUID) based on grooved Dayem bridge weak links are studied as a function of temperature: at high temperatures (60 K < T < T c = 89 K), the weak links show properties similar to superconductor-normal conductor-superconductor junctions, while at temperatures below 60 K, the weak links behave like short Dayem bridges. Using these devices, we have fabricated SQUID magnetometers with galvanically coupled in-plane pickup loops: at T = 77 K, magnetic field white noise levels as low as 63 fT/ Hz have been achieved. © 2020 Author(s).
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