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The term tunnel electroresistance (TER) denotes a fast, non-volatile, reversible resistance switching triggered by voltage pulses in ferroelectric tunnel junctions. It is explained by subtle mechanisms connected to the voltage-induced reversal of the ferroelectric polarization. Here we demonstrate that effects functionally indistinguishable from the TER can be produced in a simpler junction scheme—a direct contact between a metal and an oxide—through a different mechanism: a reversible redox reaction that modifies the oxide’s ground-state. This is shown in junctions based on a cuprate superconductor, whose ground-state is sensitive to the oxygen stoichiometry and can be tracked in operando via changes in the conductance spectra. Furthermore, we find that electrochemistry is the governing mechanism even if a ferroelectric is placed between the metal and the oxide. Finally, we extend the concept of electroresistance to the tunnelling of superconducting quasiparticles, for which the switching effects are much stronger than for normal electrons. Besides providing crucial understanding, our results provide a basis for non-volatile Josephson memory devices., The non-volatile switching of tunnel electroresistance in ferroelectric junctions provides the basis for memory and neuromorphic computing devices. Rouco et al. show tunnel electroresistance in superconductor-based junctions that arises from a redox rather than ferroelectric mechanism and is enhanced by superconductivity.

Liquid-induced phase-separation micromolding (LIPSµM) has been successfully used for manufacturing hierarchical porous polybenzimidazole (HPBI) microsieves (42-46% porosity, 30-40 µm thick) with a specific pore architecture (pattern of macropores: ~9 µm in size, perforated, dispersed in a porous matrix with a 50-100 nm pore size). Using these microsieves, proton-exchange membranes were fabricated by the infiltration of a 1H-3-vinylimidazolium bis(trifluoromethanesulfonyl)imide liquid and divinylbenzene (as a cross-linker), followed by in situ UV polymerization. Our approach relies on the separation of the ion conducting function from the structural support function. Thus, the polymeric ionic liquid (PIL) moiety plays the role of a proton conductor, whereas the HPBI microsieve ensures the mechanical resistance of the system. The influence of the porous support architecture on both proton transport performance and mechanical strength has been specifically investigated by means of comparison with straight macroporous (36% porosity) and randomly nanoporous (68% porosity) PBI counterparts. The most attractive results were obtained with the poly[1-(3H-imidazolium)ethylene]bis(trifluoromethanesulfonyl)imide PIL cross-linked with 1% divinylbenzene supported on HPBI membranes with a 21-µm-thick skin layer, achieving conductivity values up to 85 mS cm-1 at 200 °C under anhydrous conditions and in the absence of mineral acids.

In all-oxide ferroelectric (FE) - superconductor (S) bilayers, due to the low carrier concentration of oxides compared to transition metals, the FE interfacial polarization charges induce an accumulation (or depletion) of charge carriers in the S. This leads either to an enhancement or a depression of its critical temperature depending on FE polarization direction.Here we exploit this effect at a local scale to define planar weak-links in high-temperature superconducting wires. This is realized in BiFeO3(FE)/YBa2Cu3O7(S)bilayers in which the remnant FE domain structure is written at will by locally applying voltage pulses with a conductive-tip atomic force microscope. In this fashion, the FE domain pattern defines a spatial modulation of superconductivity. This allows us to write a device whose electrical transport shows different temperature regimes and magnetic field matching effects that are characteristic of Josephson coupled weak-links. This illustrates the potential of the ferroelectric approach for the realization of high-temperature superconducting devices.

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