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Leermakers I, Rubi K, Yang M, Kerdi B, Goiran M, Escoffier W, Rana AS, Smink AEM, Brinkman A, Hilgenkamp H, Maan JC, Zeitler U. Quantum oscillations in an optically-illuminated two-dimensional electron system at the LaAlO 3/SrTiO 3interface. J Phys Condens Matter 2021; 33:465002. [PMID: 34433152 DOI: 10.1088/1361-648x/ac211a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/26/2021] [Accepted: 08/25/2021] [Indexed: 06/13/2023]
Abstract
We have investigated the illumination effect on the magnetotransport properties of a two-dimensional electron system at the LaAlO3/SrTiO3interface. The illumination significantly reduces the zero-field sheet resistance, eliminates the Kondo effect at low-temperature, and switches the negative magnetoresistance into the positive one. A large increase in the density of high-mobility carriers after illumination leads to quantum oscillations in the magnetoresistance originating from the Landau quantization. The carrier density (∼2 × 1012 cm-2) and effective mass (∼1.7me) estimated from the oscillations suggest that the high-mobility electrons occupy thedxz/yzsubbands of Ti:t2gorbital extending deep within the conducting sheet of SrTiO3. Our results demonstrate that the illumination which induces additional carriers at the interface can pave the way to control the Kondo-like scattering and study the quantum transport in the complex oxide heterostructures.
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Affiliation(s)
- I Leermakers
- High Field Magnet Laboratory (HFML-EMFL) and Institute for Molecules and Materials, Radboud University, Nijmegen, The Netherlands
| | - K Rubi
- High Field Magnet Laboratory (HFML-EMFL) and Institute for Molecules and Materials, Radboud University, Nijmegen, The Netherlands
| | - M Yang
- Laboratoire National des Champs Magnétiques Intenses (LNCMI-EMFL), Université de Toulouse, CNRS, INSA, UPS, 143 Avenue de Rangueil, 31400 Toulouse, France
| | - B Kerdi
- Laboratoire National des Champs Magnétiques Intenses (LNCMI-EMFL), Université de Toulouse, CNRS, INSA, UPS, 143 Avenue de Rangueil, 31400 Toulouse, France
| | - M Goiran
- Laboratoire National des Champs Magnétiques Intenses (LNCMI-EMFL), Université de Toulouse, CNRS, INSA, UPS, 143 Avenue de Rangueil, 31400 Toulouse, France
| | - W Escoffier
- Laboratoire National des Champs Magnétiques Intenses (LNCMI-EMFL), Université de Toulouse, CNRS, INSA, UPS, 143 Avenue de Rangueil, 31400 Toulouse, France
| | - A S Rana
- MESA + Institute for Nanotechnology, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands
| | - A E M Smink
- MESA + Institute for Nanotechnology, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands
| | - A Brinkman
- MESA + Institute for Nanotechnology, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands
| | - H Hilgenkamp
- MESA + Institute for Nanotechnology, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands
| | - J C Maan
- High Field Magnet Laboratory (HFML-EMFL) and Institute for Molecules and Materials, Radboud University, Nijmegen, The Netherlands
| | - U Zeitler
- High Field Magnet Laboratory (HFML-EMFL) and Institute for Molecules and Materials, Radboud University, Nijmegen, The Netherlands
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Hilgenkamp H, Smink AEM. Suppressing superconductivity by adding it. Nat Mater 2019; 18:913-914. [PMID: 31086323 DOI: 10.1038/s41563-019-0384-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Affiliation(s)
- H Hilgenkamp
- Faculty of Science and Technology, University of Twente, Enschede, the Netherlands.
- MESA+ Institute for Nanotechnology, University of Twente, Enschede, the Netherlands.
| | - A E M Smink
- Faculty of Science and Technology, University of Twente, Enschede, the Netherlands
- MESA+ Institute for Nanotechnology, University of Twente, Enschede, the Netherlands
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Abstract
Scanning superconducting quantum interference device microscopy (SSM) is a scanning probe technique that images local magnetic flux, which allows for mapping of magnetic fields with high field and spatial accuracy. Many studies involving SSM have been published in the last few decades, using SSM to make qualitative statements about magnetism. However, quantitative analysis using SSM has received less attention. In this work, we discuss several aspects of interpreting SSM images and methods to improve quantitative analysis. First, we analyse the spatial resolution and how it depends on several factors. Second, we discuss the analysis of SSM scans and the information obtained from the SSM data. Using simulations, we show how signals evolve as a function of changing scan height, SQUID loop size, magnetization strength, and orientation. We also investigated 2-dimensional autocorrelation analysis to extract information about the size, shape, and symmetry of magnetic features. Finally, we provide an outlook on possible future applications and improvements.
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Affiliation(s)
- P Reith
- MESA+ Institute for Nanotechnology, University of Twente, P. O. Box 217, 7500 AE Enschede, The Netherlands
| | - X Renshaw Wang
- MESA+ Institute for Nanotechnology, University of Twente, P. O. Box 217, 7500 AE Enschede, The Netherlands
| | - H Hilgenkamp
- MESA+ Institute for Nanotechnology, University of Twente, P. O. Box 217, 7500 AE Enschede, The Netherlands
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Smink AEM, de Boer JC, Stehno MP, Brinkman A, van der Wiel WG, Hilgenkamp H. Gate-Tunable Band Structure of the LaAlO_{3}-SrTiO_{3} Interface. Phys Rev Lett 2017; 118:106401. [PMID: 28339281 DOI: 10.1103/physrevlett.118.106401] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/10/2016] [Indexed: 06/06/2023]
Abstract
The two-dimensional electron system at the interface between LaAlO_{3} and SrTiO_{3} has several unique properties that can be tuned by an externally applied gate voltage. In this work, we show that this gate tunability extends to the effective band structure of the system. We combine a magnetotransport study on top-gated Hall bars with self-consistent Schrödinger-Poisson calculations and observe a Lifshitz transition at a density of 2.9×10^{13}cm^{-2}. Above the transition, the carrier density of one of the conducting bands decreases with increasing gate voltage. This surprising decrease is accurately reproduced in the calculations if electronic correlations are included. These results provide a clear, intuitive picture of the physics governing the electronic structure at complex-oxide interfaces.
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Affiliation(s)
- A E M Smink
- MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - J C de Boer
- MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - M P Stehno
- MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - A Brinkman
- MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - W G van der Wiel
- MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - H Hilgenkamp
- MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
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Wang XR, Li CJ, Lu WM, Paudel TR, Leusink DP, Hoek M, Poccia N, Vailionis A, Venkatesan T, Coey JMD, Tsymbal EY, Ariando, Hilgenkamp H. Imaging and control of ferromagnetism in LaMnO3/SrTiO3 heterostructures. Science 2015; 349:716-9. [DOI: 10.1126/science.aaa5198] [Citation(s) in RCA: 129] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
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Annadi A, Zhang Q, Renshaw Wang X, Tuzla N, Gopinadhan K, Lü WM, Roy Barman A, Liu ZQ, Srivastava A, Saha S, Zhao YL, Zeng SW, Dhar S, Olsson E, Gu B, Yunoki S, Maekawa S, Hilgenkamp H, Venkatesan T, Ariando. Anisotropic two-dimensional electron gas at the LaAlO₃/SrTiO₃ (110) interface. Nat Commun 2013; 4:1838. [PMID: 23673623 PMCID: PMC3674248 DOI: 10.1038/ncomms2804] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2012] [Accepted: 03/25/2013] [Indexed: 11/15/2022] Open
Abstract
The observation of a high-mobility two-dimensional electron gas between two insulating complex oxides, especially LaAlO3/SrTiO3, has enhanced the potential of oxides for electronics. The occurrence of this conductivity is believed to be driven by polarization discontinuity, leading to an electronic reconstruction. In this scenario, the crystal orientation has an important role and no conductivity would be expected, for example, for the interface between LaAlO3 and (110)-oriented SrTiO3, which should not have a polarization discontinuity. Here we report the observation of unexpected conductivity at the LaAlO3/SrTiO3 interface prepared on (110)-oriented SrTiO3, with a LaAlO3-layer thickness-dependent metal-insulator transition. Density functional theory calculation reveals that electronic reconstruction, and thus conductivity, is still possible at this (110) interface by considering the energetically favourable (110) interface structure, that is, buckled TiO2/LaO, in which the polarization discontinuity is still present. The conductivity was further found to be strongly anisotropic along the different crystallographic directions with potential for anisotropic superconductivity and magnetism, leading to possible new physics and applications. Although LaAlO3 and SrTiO3 are both insulators, when they are brought together at a (100) interface, a highly conducting two-dimensional electron gas forms between them. Annandi et al. show that this also happens at a (110) interface, counter to expectations that it should not.
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Affiliation(s)
- A Annadi
- NUSNNI-Nanocore, National University of Singapore, Singapore 117411, Singapore
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Rusydi A, Dhar S, Barman AR, Qi DC, Motapothula M, Yi JB, Santoso I, Feng YP, Yang K, Dai Y, Yakovlev NL, Ding J, Wee ATS, Neuber G, Breese MBH, Ruebhausen M, Hilgenkamp H, Venkatesan T. Cationic-vacancy-induced room-temperature ferromagnetism in transparent, conducting anatase Ti1-xTaxO2 (x~0.05) thin films. Philos Trans A Math Phys Eng Sci 2012; 370:4927-4943. [PMID: 22987036 DOI: 10.1098/rsta.2012.0198] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We report room-temperature ferromagnetism (FM) in highly conducting, transparent anatase Ti(1-x)Ta(x)O(2) (x∼0.05) thin films grown by pulsed laser deposition on LaAlO(3) substrates. Rutherford backscattering spectrometry (RBS), X-ray diffraction, proton-induced X-ray emission, X-ray absorption spectroscopy (XAS) and time-of-flight secondary-ion mass spectrometry indicated negligible magnetic contaminants in the films. The presence of FM with concomitant large carrier densities was determined by a combination of superconducting quantum interference device magnetometry, electrical transport measurements, soft X-ray magnetic circular dichroism (SXMCD), XAS and optical magnetic circular dichroism, and was supported by first-principles calculations. SXMCD and XAS measurements revealed a 90 per cent contribution to FM from the Ti ions, and a 10 per cent contribution from the O ions. RBS/channelling measurements show complete Ta substitution in the Ti sites, though carrier activation was only 50 per cent at 5 per cent Ta concentration, implying compensation by cationic defects. The role of the Ti vacancy (V(Ti)) and Ti(3+) was studied via XAS and X-ray photoemission spectroscopy, respectively. It was found that, in films with strong FM, the V(Ti) signal was strong while the Ti(3+) signal was absent. We propose (in the absence of any obvious exchange mechanisms) that the localized magnetic moments, V(Ti) sites, are ferromagnetically ordered by itinerant carriers. Cationic-defect-induced magnetism is an alternative route to FM in wide-band-gap semiconducting oxides without any magnetic elements.
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Affiliation(s)
- A Rusydi
- NUSNNI-NanoCore, National University of Singapore, Republic of Singapore.
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Veldhorst M, Snelder M, Hoek M, Gang T, Guduru VK, Wang XL, Zeitler U, van der Wiel WG, Golubov AA, Hilgenkamp H, Brinkman A. Josephson supercurrent through a topological insulator surface state. Nat Mater 2012; 11:417-421. [PMID: 22344327 DOI: 10.1038/nmat3255] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2011] [Accepted: 01/25/2012] [Indexed: 05/31/2023]
Abstract
The long-sought yet elusive Majorana fermion is predicted to arise from a combination of a superconductor and a topological insulator. An essential step in the hunt for this emergent particle is the unequivocal observation of supercurrent in a topological phase. Here, direct evidence for Josephson supercurrents in superconductor (Nb)-topological insulator (Bi(2)Te(3))-superconductor electron-beam fabricated junctions is provided by the observation of clear Shapiro steps under microwave irradiation, and a Fraunhofer-type dependence of the critical current on magnetic field. Shubnikov-de Haas oscillations in magnetic fields up to 30 T reveal a topologically non-trivial two-dimensional surface state. This surface state is attributed to mediate the ballistic Josephson current despite the fact that the normal state transport is dominated by diffusive bulk conductivity. The lateral Nb-Bi(2)Te(3)-Nb junctions hence provide prospects for the realization of devices supporting Majorana fermions.
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van Zalk M, Brinkman A, Hilgenkamp H. Conductance anisotropy and linear magnetoresistance in La(2 - x)Sr(x)CuO4 thin films. J Phys Condens Matter 2011; 23:205602. [PMID: 21540521 DOI: 10.1088/0953-8984/23/20/205602] [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] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
We have performed a detailed study of conductance anisotropy and magnetoresistance (MR) of La(2 - x)Sr(x)CuO(4) (LSCO) thin films (0.10 < x < 0.25). These two observables are promising for the detection of stripes. Subtle features of the conductance anisotropy are revealed by measuring the transverse resistance R(xy) in zero magnetic field. It is demonstrated that the sign of R(xy) depends on the orientation of the LSCO Hall bar with respect to the terrace structure of the substrate. Unit-cell-high substrate step edges must therefore be a dominant nucleation source for antiphase boundaries during film growth. We show that the measurement of R(xy) is sensitive enough to detect the cubic-tetragonal phase transition of the SrTiO(3)(100) (STO) substrate at 105 K. The MR of LSCO thin films shows for 0.10 < x < 0.25 a non-monotonic temperature dependence, resulting from the onset of a linear term in the MR above 90 K. We show that the linear MR scales with the Hall resistivity as [Formula: see text], with the constant of proportionality independent of temperature. Such scaling suggests that the linear MR originates from current distortions induced by structural or electronic inhomogeneities. The possible role of stripes for both the MR and the conductance anisotropy is discussed throughout the paper.
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Affiliation(s)
- M van Zalk
- Faculty of Science and Technology and MESA + Institute for Nanotechnology, University of Twente, 7500 AE Enschede, The Netherlands
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Ariando, Wang X, Baskaran G, Liu ZQ, Huijben J, Yi JB, Annadi A, Barman AR, Rusydi A, Dhar S, Feng YP, Ding J, Hilgenkamp H, Venkatesan T. Electronic phase separation at the LaAlO3/SrTiO3 interface. Nat Commun 2011; 2:188. [DOI: 10.1038/ncomms1192] [Citation(s) in RCA: 347] [Impact Index Per Article: 26.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2010] [Accepted: 01/12/2010] [Indexed: 11/09/2022] Open
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Cedergren K, Kirtley JR, Bauch T, Rotoli G, Troeman A, Hilgenkamp H, Tafuri F, Lombardi F. Interplay between static and dynamic properties of semifluxons in YBa2Cu3O(7-delta) 0-pi Josephson junctions. Phys Rev Lett 2010; 104:177003. [PMID: 20482129 DOI: 10.1103/physrevlett.104.177003] [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] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2009] [Indexed: 05/29/2023]
Abstract
We have investigated the static and dynamic properties of long YBa2Cu3O(7-delta) 0-pi Josephson junctions and compared them with those of conventional 0 junctions. Scanning SQUID microscope imaging has revealed the presence of a semifluxon at the phase discontinuity point in 0-pi Josephson junctions. Zero field steps have been detected in the current-voltage characteristics of all junctions. Comparison with simulation allows us to attribute these steps to fluxons traveling in the junction for conventional 0 junctions and to fluxon-semifluxon interactions in the case of 0-pi Josephson junctions.
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Affiliation(s)
- K Cedergren
- Quantum Device Physics Laboratory, Department of Microtechnology and Nanoscience, Chalmers University of Technology, SE-412 96 Göteborg, Sweden
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Pentcheva R, Huijben M, Otte K, Pickett WE, Kleibeuker JE, Huijben J, Boschker H, Kockmann D, Siemons W, Koster G, Zandvliet HJW, Rijnders G, Blank DHA, Hilgenkamp H, Brinkman A. Parallel electron-hole bilayer conductivity from electronic interface reconstruction. Phys Rev Lett 2010; 104:166804. [PMID: 20482074 DOI: 10.1103/physrevlett.104.166804] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2009] [Indexed: 05/29/2023]
Abstract
The perovskite SrTiO3-LaAlO3 structure has advanced to a model system to investigate the rich electronic phenomena arising at polar oxide interfaces. Using first principles calculations and transport measurements we demonstrate that an additional SrTiO3 capping layer prevents atomic reconstruction at the LaAlO3 surface and triggers the electronic reconstruction at a significantly lower LaAlO3 film thickness than for the uncapped systems. Combined theoretical and experimental evidence (from magnetotransport and ultraviolet photoelectron spectroscopy) suggests two spatially separated sheets with electron and hole carriers, that are as close as 1 nm.
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Affiliation(s)
- R Pentcheva
- Department of Earth and Environmental Sciences, University of Munich, D-80333 Munich, Germany
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Mannhart J, Bielefeldt H, Goetz B, Hilgenkamp H, Schmehl A, Schneider CW, Schulz RR. Grain boundaries in high-Tc superconductors: insights and improyements. ACTA ACUST UNITED AC 2009. [DOI: 10.1080/01418630008221948] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- J. Mannhart
- a Experimental Physics VI, Center for Electronic Correlations and Magnetism, Institute of Physics, University of Augsburg , D-86135 , Augsburg , Germany
- b E-mail:
| | - H. Bielefeldt
- a Experimental Physics VI, Center for Electronic Correlations and Magnetism, Institute of Physics, University of Augsburg , D-86135 , Augsburg , Germany
| | - B. Goetz
- a Experimental Physics VI, Center for Electronic Correlations and Magnetism, Institute of Physics, University of Augsburg , D-86135 , Augsburg , Germany
| | - H. Hilgenkamp
- a Experimental Physics VI, Center for Electronic Correlations and Magnetism, Institute of Physics, University of Augsburg , D-86135 , Augsburg , Germany
| | - A. Schmehl
- a Experimental Physics VI, Center for Electronic Correlations and Magnetism, Institute of Physics, University of Augsburg , D-86135 , Augsburg , Germany
| | - C. W. Schneider
- a Experimental Physics VI, Center for Electronic Correlations and Magnetism, Institute of Physics, University of Augsburg , D-86135 , Augsburg , Germany
| | - R. R. Schulz
- a Experimental Physics VI, Center for Electronic Correlations and Magnetism, Institute of Physics, University of Augsburg , D-86135 , Augsburg , Germany
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Koster G, Brinkman A, Hilgenkamp H, Rijnders AJHM, Blank DHA. High-T(c) superconducting thin films with composition control on a sub-unit cell level; the effect of the polar nature of the cuprates. J Phys Condens Matter 2008; 20:264007. [PMID: 21694341 DOI: 10.1088/0953-8984/20/26/264007] [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] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Inspired by the work of Ohtomo and Hwang in 2004, we shed new light on thin films of layered cuprate high-T(c) superconductors (HTS). In principle all HTS materials consist of charged perovskite-like layers which in thin films can lead to polar discontinuities at the interfaces of different materials. The resulting charge redistribution has to occur but we expect it to be far more complex than in the LaAlO(3)/SrTiO(3) system since copper can be multivalent. This makes it hard to predict what will happen in terms of transport or even magnetic properties compared to the 'simple' insulator LaAlO(3). Nevertheless, we point out that the picture of systems of charged layers is important and necessary to fully understand heterostructures of these complex materials.
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Affiliation(s)
- G Koster
- MESA+ Institute of Nanotechnology and Faculty of Science and Technology, University of Twente, The Netherlands
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Brinkman A, Huijben M, van Zalk M, Huijben J, Zeitler U, Maan JC, van der Wiel WG, Rijnders G, Blank DHA, Hilgenkamp H. Magnetic effects at the interface between non-magnetic oxides. Nat Mater 2007; 6:493-6. [PMID: 17546035 DOI: 10.1038/nmat1931] [Citation(s) in RCA: 460] [Impact Index Per Article: 27.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2006] [Accepted: 05/02/2007] [Indexed: 05/15/2023]
Abstract
The electronic reconstruction at the interface between two insulating oxides can give rise to a highly conductive interface. Here we show how, in analogy to this remarkable interface-induced conductivity, magnetism can be induced at the interface between the otherwise non-magnetic insulating perovskites SrTiO3 and LaAlO3. A large negative magnetoresistance of the interface is found, together with a logarithmic temperature dependence of the sheet resistance. At low temperatures, the sheet resistance reveals magnetic hysteresis. Magnetic ordering is a key issue in solid-state science and its underlying mechanisms are still the subject of intense research. In particular, the interplay between localized magnetic moments and the spin of itinerant conduction electrons in a solid gives rise to intriguing many-body effects such as Ruderman-Kittel-Kasuya-Yosida interactions, the Kondo effect and carrier-induced ferromagnetism in diluted magnetic semiconductors. The conducting oxide interface now provides a versatile system to induce and manipulate magnetic moments in otherwise non-magnetic materials.
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Affiliation(s)
- A Brinkman
- Faculty of Science and Technology and MESA+ Institute for Nanotechnology, University of Twente, 7500 AE Enschede, The Netherlands.
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Abstract
The d-wave pairing symmetry in high-critical temperature superconductors makes it possible to realize superconducting rings with built-in pi phase shifts. Such rings have a twofold degenerate ground state that is characterized by the spontaneous generation of fractional magnetic flux quanta with either up or down polarity. We have incorporated pi phase-biased superconducting rings in a logic circuit, a flip-flop, in which the fractional flux polarity is controllably toggled by applying single flux quantum pulses at the input channel. The integration of p rings into conventional rapid single flux quantum logic as natural two-state devices should alleviate the need for bias current lines, improve device symmetry, and enhance the operation margins.
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Affiliation(s)
- T Ortlepp
- Institute of Information Technology, Rapid Single-Flux Quantum (RSFQ) Design Group, University of Technology Ilmenau, Post Office Box 100565, D-98684 Ilmenau, Germany.
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Smilde HJH, Golubov AA, Rijnders G, Dekkers JM, Harkema S, Blank DHA, Rogalla H, Hilgenkamp H. Admixtures to d-wave gap symmetry in untwinned YBa2Cu3O7 superconducting films measured by angle-resolved electron tunneling. Phys Rev Lett 2005; 95:257001. [PMID: 16390254 DOI: 10.1103/physrevlett.95.257001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2005] [Indexed: 05/06/2023]
Abstract
We report on an ab anisotropy of Jc parallel b/Jc parallel a approximately/= 1.8 IcRn parallelb/IcRn parallel a approximately/= 1.2 and in ramp-edge junctions between untwinned YBa2Cu3O7 and s-wave Nb. For these junctions, the angle theta with the YBa2Cu3O7 crystal b axis is varied as a single parameter. The RnA(theta) dependence presents twofold symmetry. The minima in IcRn at theta approximately/= 50 degrees suggest a real s-wave subdominant component and negligible d(xy)-wave or imaginary s-wave admixtures. The IcRn(theta) dependence is well fitted by 83% dx2-y2-, 15% isotropic s-, and 2% anisotropic s-wave order parameter symmetry, consistent with deltab/deltaa approximately/= 1.5.
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Affiliation(s)
- H J H Smilde
- Faculty of Science and Technology and Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
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Darminto D, Smilde HJH, Leca V, Blank DHA, Rogalla H, Hilgenkamp H. Phase-sensitive order parameter symmetry test experiments utilizing Nd(2-x)Ce(x)CuO(4-y)/Nb zigzag junctions. Phys Rev Lett 2005; 94:167001. [PMID: 15907157 DOI: 10.1103/physrevlett.94.167001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2004] [Indexed: 05/02/2023]
Abstract
Phase-sensitive order parameter symmetry test experiments are presented on the electron-doped high-T(c) cuprate Nd(2-x)Ce(x)CuO(4-y). These experiments have been conducted using zigzag-shaped thin film Josephson structures, in which the Nd(2-x)Ce(x)CuO(4-y) is connected to the low-T(c) superconductor Nb via an Au barrier layer. For the optimally doped as well as for the overdoped Nd(2-x)Ce(x)CuO(4-y), a clear predominant d(x2-y2)-wave behavior is observed at T=4.2 K. Both compounds were also investigated at T=1.6 K, presenting no indications for a change to a predominant s-wave symmetry with decreasing temperature.
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Mints RG, Papiashvili I, Kirtley JR, Hilgenkamp H, Hammerl G, Mannhart J. Observation of splintered Josephson vortices at grain boundaries in YBa(2)Cu(3)O(7-delta). Phys Rev Lett 2002; 89:067004. [PMID: 12190605 DOI: 10.1103/physrevlett.89.067004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/18/2002] [Indexed: 05/23/2023]
Abstract
We have directly observed well-separated Josephson vortex splinters with unquantized magnetic flux at asymmetric 45 degrees grain boundaries in YBa(2)Cu(3)O(7-delta) films by imaging magnetic flux with scanning SQUID microscopy. The existence of these splinter vortices has been predicted and is well described by a model based on dx(2)(-y(2)) pairing symmetry and facetting of the grain boundary on a length scale shorter than the Josephson penetration depth.
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Affiliation(s)
- R G Mints
- School of Physics and Astronomy, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Israel
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Chesca B, Schulz RR, Goetz B, Schneider CW, Hilgenkamp H, Mannhart J. d-wave induced zero-field resonances in dc pi-superconducting quantum interference devices. Phys Rev Lett 2002; 88:177003. [PMID: 12005779 DOI: 10.1103/physrevlett.88.177003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2001] [Indexed: 05/23/2023]
Abstract
A dc pi SQUID consists of a superconducting ring interrupted by two Josephson junctions, one of which carries in equilibrium a pi phase difference, caused, for example, by the d-wave pairing symmetry of the high- T(c) cuprates. If this phase shift is maintained in the voltage state, anomalous resonance currents are expected in the SQUIDs transport characteristics. Here we report the observation of such resonances for high- T(c) dc pi SQUIDs, providing evidence for the influence of the d-wave symmetry on the voltage state of a Josephson junction for frequencies of several tens of GHz.
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Affiliation(s)
- B Chesca
- Experimentalphysik VI, Center for Electronic Correlations and Magnetism, Institute of Physics, University of Augsburg, D-86135 Augsburg, Germany
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Smilde HJH, Blank DHA, Gerritsma GJ, Hilgenkamp H, Rogalla H. d-Wave-induced Josephson current counterflow in YBa2Cu3O7/Nb zigzag junctions. Phys Rev Lett 2002; 88:057004. [PMID: 11863770 DOI: 10.1103/physrevlett.88.057004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/15/2001] [Indexed: 05/23/2023]
Abstract
Well-defined zigzag-shaped ramp-type Josephson junctions between YBa2Cu3O7 and Nb have been studied. The magnetic field dependencies of the critical currents provide evidence for d-wave--induced alternations in the direction of the Josephson current between neighboring sides of the zigzag structure. The arrays present controllable model systems to study the influences of pi facets in high-angle high- T(c) grain boundaries. From the characteristics, we estimate a possible imaginary s-wave admixture to the order parameter of the YBa2Cu3O7 to be below 1%.
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Affiliation(s)
- H J H Smilde
- Low Temperature Division, Department of Applied Physics and MESA+ Research Institute, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
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Mannhart J, Hilgenkamp H, Mayer B, Gerber C, Kirtley JR, Moler KA, Sigrist M. Generation of Magnetic Flux by Single Grain Boundaries of YBa2Cu3O7-x. Phys Rev Lett 1996; 77:2782-2785. [PMID: 10062044 DOI: 10.1103/physrevlett.77.2782] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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Hilgenkamp H, Mannhart J, Mayer B. Implications of dx2-y2 symmetry and faceting for the transport properties of grain boundaries in high-Tc superconductors. Phys Rev B Condens Matter 1996; 53:14586-14593. [PMID: 9983259 DOI: 10.1103/physrevb.53.14586] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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