| 1. |
- Arpaia, Riccardo, 1985, et al.
(författare)
-
Untwinned YBa2Cu3O7-delta thin films on MgO substrates: A platform to study strain effects on the local orders in cuprates
- 2019
-
Ingår i: Physical Review Materials. - 2475-9953. ; 3:11
-
Tidskriftsartikel (refereegranskat)abstract
- We have grown untwinned YBa2Cu3O7-delta (YBCO) films on (110) MgO substrates that were preannealed at high temperature in oxygen atmosphere. The annealing results in surface reconstruction with shallow facets, which induce the suppression of the YBCO twinning domains, and the preferential alignment of the CuO chains along one of the in-plane directions of the substrate. Because of the large mismatch between the in-plane lattice parameters of film and substrate, the strain induced by the MgO into the YBCO layer is strong and very peculiar. The YBCO film is compressed, with respect to the bulk, and presents a unidirectional buckling of the atomic planes, along the chains' direction, due to a deformation of the copper-oxygen octahedra. The YBCO films, which can be grown with thicknesses down to few unit cells and oxygen doping levels spanning most of the superconducting dome, are patterned into nanowires with dimensions down to 50 nm. The anisotropies due to the untwinning state are preserved in these structures; moreover, additional anisotropies appear in ultrathin structures where strain effects become more pronounced. Such untwinned and compressively strained films can therefore be used as a platform to study the interplay between strain and the various local orders in the normal state of YBCO.
|
|
| 2. |
- Aurino, Pier Paolo, 1985, et al.
(författare)
-
Retention of Electronic Conductivity in LaAlO3/SrTiO3 Nanostructures Using a SrCuO2 Capping Layer
- 2016
-
Ingår i: Physical Review Applied. - : American Physical Society. - 2331-7019. ; 6:2
-
Tidskriftsartikel (refereegranskat)abstract
- The interface between two wide band-gap insulators, LaAlO3 and SrTiO3 (LAO/STO) offers a unique playground to study the interplay and competitions between different ordering phenomena in a strongly correlated two- dimensional electron gas. Recent studies of the LAO/STO interface reveal the inhomogeneous nature of the 2DEG that strongly influences electrical-transport properties. Nanowires needed in future applications may be adversely affected, and our aim is, thus, to produce a more homogeneous electron gas. In this work, we demonstrate that nanostructures fabricated in the quasi-2DEG at the LaAlO3/SrTiO3 interface, capped with a SrCuO2 layer, retain their electrical resistivity and mobility independent of the structure size, ranging from 100 nm to 30 mu m. This is in contrast to noncapped LAO/STO structures, where the room-temperature electrical resistivity significantly increases when the structure size becomes smaller than 1 mu m. High-resolution intermodulation electrostatic force microscopy reveals an inhomogeneous surface potential with "puddles" of a characteristic size of 130 nm in the noncapped samples and a more uniform surface potential with a larger characteristic size of the puddles in the capped samples. In addition, capped structures show superconductivity below 200 mK and nonlinear currentvoltage characteristics with a clear critical current observed up to 700 mK. Our findings shed light on the complicated nature of the 2DEG at the LAO/STO interface and may also be used for the design of electronic devices.
|
|
| 3. |
- 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.
|
|
| 4. |
- Kalaboukhov, Alexei, 1975, et al.
(författare)
-
Homogeneous superconductivity at the LaAlO3/SrTiO3 interface probed by nanoscale transport
- 2017
-
Ingår i: Physical Review B. - 2469-9969 .- 2469-9950. ; 96:18
-
Tidskriftsartikel (refereegranskat)abstract
- An interface between LaAlO3 and SrTiO3 (LAO/STO) may host two-dimensional superconductivity, strong spin-orbit coupling, and magnetic ordering. There are indications that the interfacial superconducting layer is nonhomogeneous at the nanoscale. The presence of inhomogeneities may have strong implications on the superconducting transport properties and lead to formation of weak links between superconducting regions. In this paper, we report on the temperature and magnetic field dependence of superconducting transport in single nanowires and nanorings fabricated in a LAO/STO interface. The analysis of data proves that our nanostructures behave like uniform superconducting filaments carrying a critical current close to the theoretical Ginzburg-Landau depairing limit. Furthermore, we unexpectedly find an enhancement of the critical current of LAO/STO nanowires and nanorings at low temperature when a magnetic field is applied. Our results point towards the coexistence of a homogeneous interfacial superconductivity and spatially separated magnetism at the LAO/STO interface.
|
|
| 5. |
- Manca, Nicola, et al.
(författare)
-
Strain, Young’s modulus, and structural transition of EuTiO 3 thin films probed by micro-mechanical methods
- 2023
-
Ingår i: APL Materials. - 2166-532X. ; 11:10
-
Tidskriftsartikel (refereegranskat)abstract
- EuTiO3 (ETO) is a well-known complex oxide mainly investigated for its magnetic properties and its incipient ferro-electricity. In this work, we demonstrate the realization of suspended micro-mechanical structures, such as cantilevers and micro-bridges, from 100 nm-thick single-crystal epitaxial ETO films deposited on top of SrTiO3(100) substrates. By combining profile analysis and resonance frequency measurements of these devices, we obtain the Young’s modulus, strain, and strain gradients of the ETO thin films. Moreover, we investigate the ETO anti-ferro-distortive transition by temperature-dependent characterizations, which show a non-monotonic and hysteretic mechanical response. The comparison between experimental and literature data allows us to weight the contribution from thermal expansion and softening to the tuning slope, while a full understanding of the origin of such a wide hysteresis is still missing. We also discuss the influence of oxygen vacancies on the reported mechanical properties by comparing stoichiometric and oxygen-deficient samples.
|
|
| 6. |
- Pellegrino, Luca, et al.
(författare)
-
A Hybrid Superconductor/Nanomechanical Magnetic Field Detector for Biomagnetism
- 2023
-
Ingår i: 2023 IEEE Nanotechnology Materials and Devices Conference, NMDC 2023. ; , s. 770-771
-
Konferensbidrag (refereegranskat)abstract
- We report the results of the OXiNEMS project (www.oxinems.eu) concerning the realization of a high-sensitivity magnetometer made by a magnetic nanomechanical resonator coupled to a nanopatterned superconducting thin film structure integrated with a superconducting loop. We discuss the basic working principle of the device, its first characterizations and the instrumentation we developed to measure the device performances in view of its application in the field of biomagnetism.
|
|
| 7. |
- Singh, Gyanendra, 1983, et al.
(författare)
-
Gate-tunable pairing channels in superconducting non-centrosymmetric oxides nanowires
- 2022
-
Ingår i: npj Quantum Materials. - : Springer Science and Business Media LLC. - 2397-4648. ; 7:1
-
Tidskriftsartikel (refereegranskat)abstract
- Two-dimensional SrTiO3-based interfaces stand out among non-centrosymmetric superconductors due to their intricate interplay of gate-tunable Rashba spin-orbit coupling and multi-orbital electronic occupations, whose combination theoretically prefigures various forms of non-standard superconductivity. By employing superconducting transport measurements in nano-devices we present strong experimental indications of unconventional superconductivity in the LaAlO3/SrTiO3 interface. The central observations are the substantial anomalous enhancement of the critical current by small magnetic fields applied perpendicularly to the plane of electron motion, and the asymmetric response with respect to the magnetic field direction. These features cannot be accommodated within a scenario of canonical spin-singlet superconductivity. We demonstrate that the experimental observations can be described by a theoretical model based on the coexistence of Josephson channels with intrinsic phase shifts. Our results exclude a time-reversal symmetry breaking scenario and suggest the presence of anomalous pairing components that are compatible with inversion symmetry breaking and multi-orbital physics.
|
|
| 8. |
- Singh, Gyanendra, 1983, et al.
(författare)
-
Nanopatterning of weak links in superconducting oxide interfaces
- 2021
-
Ingår i: Nanomaterials. - : MDPI AG. - 2079-4991. ; 11:2, s. 1-11
-
Tidskriftsartikel (refereegranskat)abstract
- The interface between two wide band-gap insulators, LaAlO3 and SrTiO3 (LAO/STO), hosts a quasi-two-dimensional electron gas (q2DEG), two-dimensional superconductivity, ferromagnetism, and giant Rashba spin-orbit coupling. The co-existence of two-dimensional superconductivity with gate-tunable spin-orbit coupling and multiband occupation is of particular interest for the realization of unconventional superconducting pairing. To investigate the symmetry of the superconducting order parameter, phase sensitive measurements of the Josephson effect are required. We describe an approach for the fabrication of artificial superconducting weak links at the LAO/STO interface using direct high-resolution electron beam lithography and low-energy argon ion beam irradiation. The method does not require lift-off steps or sacrificial layers. Therefore, resolution is only limited by the electron beam lithography and pattern transfer. We have realized superconducting weak links with a barrier thickness of 30–100 nm. The barrier transparency of the weak links can be controlled by the irradiation dose and further tuned by a gate voltage. Our results open up new possibilities for the realization of quantum devices in oxide interfaces.
|
|
| 9. |
- Trabaldo, Edoardo, 1990, et al.
(författare)
-
Grooved Dayem Nanobridges as Building Blocks of High-Performance YBa2Cu3O7−δ SQUID Magnetometers
- 2019
-
Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 19:3, s. 1902-1907
-
Tidskriftsartikel (refereegranskat)abstract
- We present noise measurements performed on a YBa 2 Cu 3 O 7-δ nanoscale weak-link-based magnetometer consisting of a superconducting quantum interference device (SQUID) galvanically coupled to a 3.5 × 3.5 mm 2 pick-up loop, reaching white flux noise levels and magnetic noise levels as low as 6μÎ0/Hz and 100 fT/Hz at T = 77 K, respectively. The low noise is achieved by introducing grooved Dayem bridges (GDBs), a new concept of a weak link. A fabrication technique has been developed for the realization of nanoscale grooved bridges, which substitutes standard Dayem bridge weak links. The introduction of these novel key blocks reduces the parasitic inductance of the weak links and increases the differential resistance of the SQUIDs. This greatly improves the device performance, thus resulting in a reduction of the white noise.
|
|
| 10. |
- Trabaldo, Edoardo, 1990, et al.
(författare)
-
Mapping the Phase Diagram of a YBa2Cu3 O7-δ Nanowire Through Electromigration
- 2022
-
Ingår i: Physical Review Applied. - 2331-7019. ; 17:2
-
Tidskriftsartikel (refereegranskat)abstract
- We use electromigration (EM) to tune the oxygen content of YBa2Cu3O7-δ (YBCO) nanowires. During EM, the dopant oxygen atoms in the nanowire are moved under the combined effect of electrostatic force and Joule heating. The EM current can be tuned to either deplete or replenish nanowires with oxygen, allowing fine tuning of its hole-doping level. Electrical transport measurements and Kelvin probe microscopy corroborate good homogeneity of the doping level along the electromigrated nanowires. Thus, EM provides an effective method to study transport properties of YBCO in a wide doping range at the nanoscale in one and the same device.
|
|
