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Singh G, Lesne E, Winkler D, Claeson T, Bauch T, Lombardi F, Caviglia AD, Kalaboukhov A. Nanopatterning of Weak Links in Superconducting Oxide Interfaces. Nanomaterials (Basel) 2021; 11:398. [PMID: 33557305 PMCID: PMC7914727 DOI: 10.3390/nano11020398] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/30/2020] [Revised: 01/22/2021] [Accepted: 01/28/2021] [Indexed: 11/16/2022]
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.
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Affiliation(s)
- Gyanendra Singh
- Department of Microtechnology and Nanoscience—MC2, Chalmers University of Technology, SE 412 96 Gothenburg, Sweden; (G.S.); (D.W.); (T.C.); (T.B.); (F.L.)
| | - Edouard Lesne
- Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands; (E.L.); (A.D.C.)
| | - Dag Winkler
- Department of Microtechnology and Nanoscience—MC2, Chalmers University of Technology, SE 412 96 Gothenburg, Sweden; (G.S.); (D.W.); (T.C.); (T.B.); (F.L.)
| | - Tord Claeson
- Department of Microtechnology and Nanoscience—MC2, Chalmers University of Technology, SE 412 96 Gothenburg, Sweden; (G.S.); (D.W.); (T.C.); (T.B.); (F.L.)
| | - Thilo Bauch
- Department of Microtechnology and Nanoscience—MC2, Chalmers University of Technology, SE 412 96 Gothenburg, Sweden; (G.S.); (D.W.); (T.C.); (T.B.); (F.L.)
| | - Floriana Lombardi
- Department of Microtechnology and Nanoscience—MC2, Chalmers University of Technology, SE 412 96 Gothenburg, Sweden; (G.S.); (D.W.); (T.C.); (T.B.); (F.L.)
| | - Andrea D. Caviglia
- Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands; (E.L.); (A.D.C.)
| | - Alexei Kalaboukhov
- Department of Microtechnology and Nanoscience—MC2, Chalmers University of Technology, SE 412 96 Gothenburg, Sweden; (G.S.); (D.W.); (T.C.); (T.B.); (F.L.)
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Chikina A, Lechermann F, Husanu MA, Caputo M, Cancellieri C, Wang X, Schmitt T, Radovic M, Strocov VN. Orbital Ordering of the Mobile and Localized Electrons at Oxygen-Deficient LaAlO 3/SrTiO 3 Interfaces. ACS Nano 2018; 12:7927-7935. [PMID: 29995384 DOI: 10.1021/acsnano.8b02335] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Interfacing different transition-metal oxides opens a route to functionalizing their rich interplay of electron, spin, orbital, and lattice degrees of freedom for electronic and spintronic devices. Electronic and magnetic properties of SrTiO3-based interfaces hosting a mobile two-dimensional electron system (2DES) are strongly influenced by oxygen vacancies, which form an electronic dichotomy, where strongly correlated localized electrons in the in-gap states (IGSs) coexist with noncorrelated delocalized 2DES. Here, we use resonant soft-X-ray photoelectron spectroscopy to prove the eg character of the IGSs, as opposed to the t2g character of the 2DES in the paradigmatic LaAlO3/SrTiO3 interface. We furthermore separate the d xy and d xz/d xz orbital contributions based on deeper consideration of the resonant photoexcitation process in terms of orbital and momentum selectivity. Supported by a self-consistent combination of density functional theory and dynamical mean field theory calculations, this experiment identifies local orbital reconstruction that goes beyond the conventional eg- vs-t2g band ordering. A hallmark of oxygen-deficient LaAlO3/SrTiO3 is a significant hybridization of the eg and t2g orbitals. Our findings provide routes for tuning the electronic and magnetic properties of oxide interfaces through "defect engineering" with oxygen vacancies.
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Affiliation(s)
- Alla Chikina
- Swiss Light Source, Paul Scherrer Institute , Villigen CH-5232 , Switzerland
| | - Frank Lechermann
- Institut für Theoretische Physik , Universität Hamburg , Jungiusstrasse 9 , Hamburg DE-20355 , Germany
| | - Marius-Adrian Husanu
- Swiss Light Source, Paul Scherrer Institute , Villigen CH-5232 , Switzerland
- National Institute of Materials Physics , Atomistilor 405A , Magurele RO-077125 , Romania
| | - Marco Caputo
- Swiss Light Source, Paul Scherrer Institute , Villigen CH-5232 , Switzerland
| | - Claudia Cancellieri
- Swiss Light Source, Paul Scherrer Institute , Villigen CH-5232 , Switzerland
- Empa, Swiss Federal Laboratories for Materials Science & Technology , Ueberlandstrasse 129 , Duebendorf CH-8600 , Switzerland
| | - Xiaoqiang Wang
- Swiss Light Source, Paul Scherrer Institute , Villigen CH-5232 , Switzerland
| | - Thorsten Schmitt
- Swiss Light Source, Paul Scherrer Institute , Villigen CH-5232 , Switzerland
| | - Milan Radovic
- Swiss Light Source, Paul Scherrer Institute , Villigen CH-5232 , Switzerland
| | - Vladimir N Strocov
- Swiss Light Source, Paul Scherrer Institute , Villigen CH-5232 , Switzerland
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Mattoni G, Baek DJ, Manca N, Verhagen N, Groenendijk DJ, Kourkoutis LF, Filippetti A, Caviglia AD. Insulator-to-Metal Transition at Oxide Interfaces Induced by WO 3 Overlayers. ACS Appl Mater Interfaces 2017; 9:42336-42343. [PMID: 29111647 DOI: 10.1021/acsami.7b13202] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Interfaces between complex oxides constitute a unique playground for two-dimensional electron systems (2DESs), where superconductivity and magnetism can arise from combinations of bulk insulators. The 2DES at the LaAlO3/SrTiO3 interface is one of the most studied in this regard, and its origin is determined by the polar field in LaAlO3 as well as by the presence of point defects, like oxygen vacancies and intermixed cations. These defects usually reside in the conduction channel and are responsible for a decrease of the electronic mobility. In this work, we use an amorphous WO3 overlayer to obtain a high-mobility 2DES in WO3/LaAlO3/SrTiO3 heterostructures. The studied system shows a sharp insulator-to-metal transition as a function of both LaAlO3 and WO3 layer thickness. Low-temperature magnetotransport reveals a strong magnetoresistance reaching 900% at 10 T and 1.5 K, the presence of multiple conduction channels with carrier mobility up to 80 000 cm2 V-1 s-1, and quantum oscillations of conductance.
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Affiliation(s)
- Giordano Mattoni
- Kavli Institute of Nanoscience, Delft University of Technology , 2628 CJ Delft, The Netherlands
| | | | - Nicola Manca
- Kavli Institute of Nanoscience, Delft University of Technology , 2628 CJ Delft, The Netherlands
| | - Nils Verhagen
- Kavli Institute of Nanoscience, Delft University of Technology , 2628 CJ Delft, The Netherlands
| | - Dirk J Groenendijk
- Kavli Institute of Nanoscience, Delft University of Technology , 2628 CJ Delft, The Netherlands
| | | | - Alessio Filippetti
- Dipartimento di Fisica, Università di Cagliari , Cagliari, Monserrato 09042-I, Italy
- CNR-IOM, Istituto Officina dei Materiali, Cittadella Universitaria , Cagliari, Monserrato 09042-I, Italy
| | - Andrea D Caviglia
- Kavli Institute of Nanoscience, Delft University of Technology , 2628 CJ Delft, The Netherlands
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