Abstract
The two-dimensional superconductor that forms at the interface between the complex oxides lanthanum aluminate (LAO) and strontium titanate (STO)1 has several intriguing properties2,3,4,5,6 that set it apart from conventional superconductors. Most notably, an electric field can be used to tune its critical temperature (Tc; ref. 7), revealing a dome-shaped phase diagram reminiscent of high-Tc superconductors8. So far, experiments with oxide interfaces have measured quantities that probe only the magnitude of the superconducting order parameter and are not sensitive to its phase. Here, we perform phase-sensitive measurements by realizing the first superconducting quantum interference devices (SQUIDs) at the LAO/STO interface. Furthermore, we develop a new paradigm for the creation of superconducting circuit elements, where local gates enable the in situ creation and control of Josephson junctions. These gate-defined SQUIDs are unique in that the entire device is made from a single superconductor with purely electrostatic interfaces between the superconducting reservoir and the weak link. We complement our experiments with numerical simulations and show that the low superfluid density of this interfacial superconductor results in a large, gate-controllable kinetic inductance of the SQUID. Our observation of robust quantum interference opens up a new pathway to understanding the nature of superconductivity at oxide interfaces.
This is a preview of subscription content, access via your institution
Access options
Subscribe to this journal
Receive 12 print issues and online access
$259.00 per year
only $21.58 per issue
Buy this article
- Purchase on Springer Link
- Instant access to full article PDF
Prices may be subject to local taxes which are calculated during checkout
Similar content being viewed by others
References
Reyren, N. et al. Superconducting interfaces between insulating oxides. Science 317, 1196–1199 (2007).
Caviglia, A. D. et al. Tunable Rashba spin-orbit interaction at oxide interfaces. Phys. Rev. Lett. 104, 126803 (2010).
Ben Shalom, M. et al. Tuning spin-orbit coupling and superconductivity at the LaAlO3/SrTiO3 interface: a magnetotransport study. Phys. Rev. Lett. 104, 126802 (2010).
Dikin, D. A. et al. Coexistence of superconductivity and ferromagnetism in two dimensions. Phys. Rev. Lett. 107, 056802 (2011).
Bert, J. A. et al. Direct imaging of the coexistence of ferromagnetism and superconductivity at the LaAlO3/SrTiO3 interface. Nature Phys. 7, 767–771 (2011).
Li, L. et al. Coexistence of magnetic order and two-dimensional superconductivity at LaAlO3/SrTiO3 interfaces. Nature Phys. 7, 762–766 (2011).
Caviglia, A. D. et al. Electric field control of the LaAlO3/SrTiO3 interface ground state. Nature 456, 624–627 (2008).
Richter, C. et al. Interface superconductor with gap behaviour like a high-temperature superconductor. Nature 502, 528–531 (2013).
Ryazanov, V. V. et al. Coupling of two superconductors through a ferromagnet: evidence for a π junction. Phys. Rev. Lett. 86, 2427–2430 (2001).
Weides, M. et al. 0-π Josephson tunnel junctions with ferromagnetic barrier. Phys. Rev. Lett. 97, 247001 (2006).
Veldhorst, M. et al. Josephson supercurrent through a topological insulator surface state. Nature Mater. 11, 417–421 (2012).
van Dam, J. A. et al. Supercurrent reversal in quantum dots. Nature 442, 667–670 (2006).
Nelson, K. D. et al. Odd-parity superconductivity in Sr2RuO4 . Science 306, 1151–1154 (2004).
van Harlingen, D. J. Phase-sensitive tests of the symmetry of the pairing state in the high-temperature superconductors−evidence for d x 2 - y 2 symmetry. Rev. Mod. Phys. 67, 515–535 (1995).
Cheng, G. et al. Electron pairing without superconductivity. Nature 521, 196–199 (2015).
Takayanagi, H. & Kawakami, T. Superconducting proximity effect in the native inversion layer on InAs. Phys. Rev. Lett. 54, 2449–2452 (1985).
Doh, Y.-J. et al. Tunable supercurrent through semiconductor nanowires. Science 309, 272–275 (2005).
Heersche, H. B. et al. Bipolar supercurrent in graphene. Nature 446, 56–59 (2007).
Brandt, E. H. & Clem, J. R. Superconducting thin rings with finite penetration depth. Phys. Rev. B 69, 184509 (2004).
Khapaev, M. M. et al. Current distribution simulation for superconducting multi-layered structures. Supercond. Sci. Technol. 16, 24 (2003).
Reyren, N. et al. Anisotropy of the superconducting transport properties of the LaAlO3/SrTiO3 interface. Appl. Phys. Lett. 94, 112506 (2009).
Bert, J. A. et al. Gate-tuned superfluid density at the superconducting LaAlO3/SrTiO3 interface. Phys. Rev. B 86, 060503 (2012).
McCollam, A. et al. Quantum oscillations and subband properties of the two-dimensional electron gas at the LaAlO3/SrTiO3 interface. APL Mater. 2, 022102 (2014).
Tinkham, M. Introduction to Superconductivity 2nd edn (Dover, 1996).
Gallagher, P. et al. Gate-tunable superconducting weak link and quantum point contact spectroscopy on a strontium titanate surface. Nature Phys. 10, 748–752 (2014).
Goswami, S. et al. Nanoscale electrostatic control of oxide interfaces. Nano Lett. 15, 2627–2632 (2015).
Bal, V. V. et al. Gate-tunable superconducting weak link behavior in top-gated LaAlO3-SrTiO3 . Appl. Phys. Lett. 106, 212601 (2015).
Clarke, J. & Braginski, A. I. (eds) The SQUID Handbook Vol. 1 (Wiley, 2004).
Honig, M. et al. Local electrostatic imaging of striped domain order in LaAlO3/SrTiO3 . Nature Mater. 12, 1112–1118 (2013).
Kalisky, B. et al. Locally enhanced conductivity due to the tetragonal domain structure in LaAlO3/SrTiO3 heterointerfaces. Nature Mater. 12, 1091–1095 (2013).
Acknowledgements
We thank T. Klapwijk, A. Geresdi, A. Akhmerov, A. Brinkman and J. Mannhart for useful discussions and feedback about the preliminary results. This work was supported by The Netherlands Organisation for Scientific Research (NWO/OCW) as part of the Frontiers of Nanoscience program, the Dutch Foundation for Fundamental Research on Matter (FOM), the Deutsche Forschungsgemeinschaft (DFG) via Project KO 1303/13-1 and EU-FP6-COST Action MP1308.
Author information
Authors and Affiliations
Contributions
E.M. fabricated the devices. S.G. performed the transport measurements with help from E.M. S.G. and A.M.R.V.L.M. analysed the data. R.W., R.K. and D.K. carried out the numerical simulations and Y.M.B. provided theoretical support. L.M.K.V. and A.D.C. supervised the project. S.G. wrote the manuscript with input from all co-authors.
Corresponding authors
Ethics declarations
Competing interests
The authors declare no competing financial interests.
Supplementary information
Supplementary information
Supplementary information (PDF 916 kb)
Rights and permissions
About this article
Cite this article
Goswami, S., Mulazimoglu, E., Monteiro, A. et al. Quantum interference in an interfacial superconductor. Nature Nanotech 11, 861–865 (2016). https://doi.org/10.1038/nnano.2016.112
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1038/nnano.2016.112
This article is cited by
-
Superconducting tunnel junctions with layered superconductors
Quantum Frontiers (2024)
-
A tunable monolithic SQUID in twisted bilayer graphene
Nature Nanotechnology (2022)
-
Dynamic properties of high-Tc superconducting nano-junctions made with a focused helium ion beam
Scientific Reports (2020)
-
Transport regimes of a split gate superconducting quantum point contact in the two-dimensional LaAlO3/SrTiO3 superfluid
Nature Communications (2018)
-
Imaging and tuning polarity at SrTiO3 domain walls
Nature Materials (2017)