| 1. |
- Arpaia, Riccardo, 1985, et al.
(författare)
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Highly homogeneous YBCO/LSMO nanowires for photoresponse experiments
- 2014
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Ingår i: Superconductor Science and Technology. - : IOP Publishing. - 0953-2048 .- 1361-6668. ; 27:4
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Tidskriftsartikel (refereegranskat)abstract
- By using nanolithography and a soft etching procedure, we have realized YBa2Cu3O7-x/La0.7Sr0.3MnO3 (YBCO/LSMO) nanowires, with cross sections down to 100 x 50 nm(2) that ensure the cover age of areas up to 10 x 30 mu m(2). The LSMO layer acts as a capping for YBCO, minimizing the degradation of the superconducting properties taking place during the patterning; moreover, as a ferromagnetic manganite, it is expected to accelerate the relaxation dynamics of quasiparticles in YBCO, making such a system potentially attractive for applications in superconducting ultrafast optoelectronics. The reproducibility of the values of the critical current densities measured in different devices with the same geometry makes our nanowires ideal candidates for photoresponse experiments. First measurements have shown a satisfactory photoresponse from YBCO/LSMO devices.
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| 2. |
- Arpaia, Riccardo, 1985, et al.
(författare)
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Improved Nanopatterning for YBCO Nanowires Approaching the Depairing Current
- 2013
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Ingår i: IEEE Transactions on Applied Superconductivity. - : Institute of Electrical and Electronics Engineers (IEEE). - 1558-2515 .- 1051-8223. ; 23:3
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Tidskriftsartikel (refereegranskat)abstract
- An improved nanopatterning procedure has been developed to obtain YBa2Cu3O7-x nanowires with cross-sections as small as 50 x 50 nm(2), protected by an Au capping layer. To probe the effective role of the Au protecting layer, we have measured the current-voltage characteristics and the resistive transition in temperature of the nanowires. Critical current densities up to 108 A/cm(2) have been achieved at T = 4.2 K, approaching the theoretical depairing current limit. The resistance, measured as a function of temperature close to T-c, has been fitted with a thermal activated phase slip model, including the effect of the gold layer. The extracted values of the superconducting coherence length and of the London penetration depth give current densities consistent with the measured ones. These results cannot be achieved with nanowires without the Au capping layer.
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| 3. |
- Arpaia, Riccardo, 1985, et al.
(författare)
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Resistive state triggered by vortex entry in YBa2Cu3O7-delta nanostructures
- 2014
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Ingår i: Physica C: Superconductivity and its Applications. - : Elsevier BV. - 0921-4534. ; 506, s. 165-168
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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)
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Ultra low noise YBa2Cu3O7-delta nano superconducting quantum interference devices implementing nanowires
- 2014
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 104:7
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Tidskriftsartikel (refereegranskat)abstract
- We present results on ultra low noise YBa2Cu3O7-delta (YBCO) nano Superconducting QUantum Interference Devices (nanoSQUIDs). To realize such devices, we implemented high quality YBCO nanowires, working as weak links between two electrodes. We observe critical current modulation as a function of an externally applied magnetic field in the full temperature range below the transition temperature T-C. The white flux noise below 1 mu Phi(0)/root Hz at T = 8K makes our nanoSQUIDs very attractive for the detection of small spin systems.
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| 5. |
- Bauch, Thilo, 1972, et al.
(författare)
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High critical temperature superconductor Josephson junctions for quantum circuit applications
- 2009
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Ingår i: Physica Scripta. ; T137, s. 014006-
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Konferensbidrag (refereegranskat)abstract
- Recent findings of macroscopic quantum properties in high critical temperature superconductor (HTS) Josephson junctions (JJs) point toward the need to revise the role of zero energy quasi-particles in this novel superconductor. We will discuss the possibility of designing superconducting artificial atoms in a transmon configuration to study the low energy excitation spectra of HTS. We have engineered high quality grain boundary JJs on low dielectric constant substrates. By fabricating submicron junctions, we extract values of capacitance and Josephson critical current densities that satisfy the main transmon design requirements. Moreover, the measured critical current noise power extrapolated at 1 Hz gives a dephasing time of 25 ns, which indicates that the observation of macroscopic quantum coherent effects in HTS JJ is a feasible task.
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| 6. |
- Gustafsson, David, 1982, et al.
(författare)
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Low capacitance HTS junctions for single electron transistors
- 2009
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Ingår i: Physica C: Superconductivity and its Applications. - : Elsevier BV. - 0921-4534. ; 470:SUPPL.1, s. S188-S190
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Konferensbidrag (refereegranskat)abstract
- We have fabricated and characterized YBa2Cu3O7-δ grain boundary junctions to determine their feasibility as tunnel barriers in single electron transistors. Superconducting quantum interference devices with injection lines have been used to measure the junctions capacitance. We have extracted capacitance values which allow us to achieve a Coulomb blockade regime for sufficiently small junction dimensions.
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| 7. |
- Nawaz, Shahid, 1978, et al.
(författare)
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Approaching the theoretical depairing current in YBa2Cu3O7-x nanowires
- 2013
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Ingår i: Physica C: Superconductivity and its Applications. - : Elsevier BV. - 0921-4534. ; 495, s. 33-38
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Tidskriftsartikel (refereegranskat)abstract
- YBa2Cu3O7-x nanowires, with lateral dimensions smaller that 50 nm have been fabricated by a soft etching procedure preserving an Au capping layer on top of the nanostructure. We have obtained YBCO nanowires carrying critical current densities J(c) close to the theoretical depairing limit. The resistive transition and the J(c) as a function of temperature of the Au capped nanostructures have been compared with those where the Au protective layer was subsequently removed. We conclude that the Au capping layer together with the soft etching procedure are instrumental in preserving shape pristine superconducting properties very close to the as grown film. Our results open new perspective for the use of YBCO nanostructures in fundamental studies aiming at shedding light on the mechanism for high critical temperature superconductivity. (C) 2013 Elsevier B.V. All rights reserved.
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| 8. |
- Nawaz, Shahid, 1978, et al.
(författare)
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Microwave Response of Superconducting YBa2Cu3O7-delta Nanowire Bridges Sustaining the Critical Depairing Current: Evidence of Josephson-like Behavior
- 2013
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Ingår i: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 110:16, s. 167004-
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Tidskriftsartikel (refereegranskat)abstract
- We have investigated the zero-field critical supercurrent of YBa2Cu3O7-delta bridges patterned from 50 nm thick films as a function of bridge width, ranging from 2 mu m to 50 nm. The critical current density monotonically increases for decreasing bridge width even for widths smaller than the Pearl length. This behavior is accounted for by considering current crowding effects at the junction between the bridge and the wider electrodes. Comparison to numerical calculations of the current distributions in our bridge geometries of various widths yields a (local) critical current density at 4.2 K of 1.3 x 10(8) Lambda/cm(2), the Ginzburg Landau depairing current density. The observation of up to 160 Shapiro-like steps in the current voltage characteristics under microwave irradiation substantiates the pristine character of our nanobridges with cross sections as small as 50 x 50 nm(2).
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| 9. |
- Nawaz, Shahid, 1978, et al.
(författare)
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Transport Properties of YBCO Nanowires
- 2011
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Ingår i: IEEE Transactions on Applied Superconductivity. - : Institute of Electrical and Electronics Engineers (IEEE). - 1558-2515 .- 1051-8223. ; 21:3, s. 164-167
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Tidskriftsartikel (refereegranskat)abstract
- We have carried out transport studies of YBa2Cu3O7-x (YBCO) nanowires. By exposing nanowires with microwaves, we see that short wires which have a flux-flow like current-voltage characteristic (IVC) clearly manifest current steps in the IVC (Shapiro steps). On the contrary, the longer wires exhibiting a resistively and capacitively shunted junction (RCSJ) model like current-voltage characteristic do not feature any Shapiro steps. The second case can be explained by taking into consideration the longer wire lengths where the wires loose coherency of flux flow due to inhomogeneity along the wire.
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