R49.00005. Tunneling spectroscopy of c-axis epitaxial cuprate junctions

Presented by: Douglas Natelson


Abstract

Tunnel junctions are valuable tools for electronic spectroscopy, with epitaxial structures minimizing extrinsic effects of disorder. We report tunneling spectroscopy measurements, over a broad temperature and bias range, in c-axis La2−xSrxCuO4/La2CuO4/La2−xSrxCuO4 heterostructures grown via atomic layer-by-layer molecular beam epitaxy. Above Tc of the LSCO layers, these structures show the pseudogap, while below Tc, the devices show superconductor/insulator/superconductor (SIS) response. Down to 20 mK there is no Josephson critical supercurrent Ic, indicating strongly incoherent transport. Tunneling spectra show greatly suppressed coherence peaks. The T=0 zero-bias conductance remains at approximately 20-30% that of the normal-state, implying a substantial population of unpaired carriers. As temperature is raised, the superconducting gap fills in rather than closing at Tc. The spectra show an inelastic tunneling feature at ∼0.08 eV, suppressed as T exceeds Tc. We discuss how these properties are inconsistent with standard d-wave tunneling expectations, despite the structural perfection of the epitaxial stack.

Authors

  • Panpan Zhou
  • Liyang Chen
  • Ilya Sochnikov
  • Tsz Chun Wu
  • Matthew S. Foster
  • Anthony T. Bollinger
  • Xi He
  • Ivan Bozovic


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