| 1. |
- 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.
|
|
| 2. |
- 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.
|
|
| 3. |
- 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.
|
|
| 4. |
- 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.
|
|
| 5. |
- Stepantsov, Evgeni, 1951, et al.
(författare)
-
Growth of YBa2Cu3O7 films with 100 tilt of CuO planes to the surface on SrTiO3 crystals
- 2011
-
Ingår i: Crystallography Reports. - : Pleiades Publishing Ltd. - 1562-689X .- 1063-7745. ; 56:1, s. 152-156
-
Tidskriftsartikel (refereegranskat)abstract
- YBa2Cu3O7 films with CuO planes tilted to the surface have been grown on SrTiO3 crystals by pulsed laser deposition. The tilt angle was varied in the range from 0A degrees (CuO planes are parallel to the surface) to 70A degrees. At this tilt, the crystalline lattice of the film was rotated by rotating the substrate crystalline lattice around its axis [100], which is oriented parallel to the surface. The zero tilt of CuO planes corresponds to the orientation of the SrTiO3 surface parallel to the (100) plane. It is established that the CuO planes of the film remain parallel to one or several (100)-type planes of the substrate at an arbitrary tilt angle. In the range of tilt angles from 0A degrees to 41A degrees, the film has a single-crystal structure. At tilt angles above 41A degrees, the film is transformed into a two-domain texture and its surface roughness sharply increases.
|
|
| 6. |
- Stepantsov, Evgeni, 1951, et al.
(författare)
-
Growth of YBa2Cu3O7 films with [110] tilt of CuO planes to surface on SrTiO3 crystals
- 2013
-
Ingår i: Crystallography Reports. - 1562-689X .- 1063-7745. ; 58:3, s. 488-492
-
Tidskriftsartikel (refereegranskat)abstract
- YBa2Cu3O7 films with the CuO plane tilted to the surface have been grown on SrTiO3 crystalline substrates by pulsed laser deposition. This tilt was obtained by rotating the film lattice with respect to the substrate surface around its [110] axis oriented parallel to the surface. The zero tilt of the CuO plane was implemented at the orientation of the SrTiO3 crystal surface parallel to the (100) plane. The rotation angles were varied in the range from 0A degrees to 70A degrees. It is found that, being tilted at any angle, the CuO planes of the film remain parallel to one or several crystallographic planes of the (100)-type substrate. In the range of tilt angles from 0A degrees to 49A degrees, the film has a single-crystal structure. Above 49A degrees the film is transformed into a three-domain texture and its surface roughness sharply increases.
|
|
| 7. |
- Sukhorukov, Y. P., et al.
(författare)
-
Effect of an interface boundary on the magnetooptical and magnetotransport properties of La0.67Ca0.33MnO3/La0.67Sr0.33MnO3 heterostructures
- 2010
-
Ingår i: Technical Physics. - 1063-7842 .- 1090-6525. ; 55:8, s. 1161-1167
-
Tidskriftsartikel (refereegranskat)abstract
- The optical, magnetooptical (Kerr effect and magnetotransmission), and magnetotransport properties of La2/3Ca1/3MnO3/La2/3Sr1/3MnO3 and La2/3Ca1/3MnO3/SrTiO3/La2/3Sr1/3MnO3 heterostructures on SrTiO3 substrates are studied. The contribution of the interface boundary to the magnetotransmission is typical of a material with a transitional composition. It is found that a 2-nm-thick SrTiO3 spacer does not influence the shape and position of the magnetotransmission peak in a field normal to the surface of the heterostructure but increases the contribution of the upper layer to the magnetotransmission in the Voigt geometry and also enhances the magnetoresistance that is due to the tunneling of spin-polarized carriers through the spacer. The Kerr spectra taken of the heterostructures are typical of single-layer single-crystal films.
|
|
| 8. |
- Sukhorukov, Y. P., et al.
(författare)
-
Magnetorefractive and Kerr effects in the La0.67Ca0.33MnO3/La0.67Sr0.33MnO3 (n) superlattices
- 2014
-
Ingår i: Superlattices and Microstructures. - : Elsevier BV. - 0749-6036 .- 1096-3677. ; 75, s. 680-691
-
Tidskriftsartikel (refereegranskat)abstract
- It is demonstrated that in the [La0.67Ca0.33MnO3(d = 9 nm)/La0.67Sr0.33MnO3(9 nm)](3) and [La0.67Ca0.33MnO3(9 nm)/SrTiO3(2 nm)/La0.67Sr0.33MnO3(9 nm)](3) superlattices with the interlayer barriers of nonmagnetic dielectric SrTiO3, the magneto-optical Kerr and magnetorefraction (magnetoreflection and magnetotransmission of unpolarized light) effects have large values close to those for the heterostructures of the same composition. The defects and strain in the layers and at interfaces of superlattices result in appearance of additional band in the Kerr effect spectrum, temperature hysteresis, and abnormal temperature dependence of the Kerr effect. It is shown, that the resonant-like contribution to the magnetoreflection spectra of superlattices is due to the shift of the minima in reflection coefficient near the phonon bands by magnetic field. The increase in magnetotransmission of superlattices relative to a single layered film is due to multiple transmission of light through the layers of superlattices. The intermixing effects at interfaces and deviations of composition of layers from stoichiometry both influence the values of magnetorefraction effect in superlattices and the shapes of their temperature dependences.
|
|
| 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)
-
Properties of grooved Dayem bridge based YBa2Cu3 O 7 - δ superconducting quantum interference devices and magnetometers
- 2020
-
Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 116:13
-
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).
|
|
