High Temperature Interfacial Superconductivity
(a) Annular dark field image of the structure showing extended defects in the metal layer (marked by white arrows). The black arrow shows the metal-insulator interface (b) A magnified image of one defect which nucleated at the cuprate-substrate interface and is due to local variations in the termination layer of the substrate.
Cuprate superconductors exhibit relatively high transition temperatures, but their unit cells are complex and large. Localizing a superconducting layer to a small thickness is difficult with bulk cuprates due to the challenges of growing layers with precise thicknesses. The inventive structures can be used to make superconducting field effect transistors (SuFETs), using the interfacial superconducting layer as the channel.Description
Superconducting structures displaying stable interface superconductivity at relatively high temperatures, 15K to 50K have been developed. The effect is observed between two components even when neither is, itself, superconducting. Superconducting properties in these structures, such as the transition temperature, can be altered by a number of methods, including: altering the composition of one or both components; changing the thickness of one or more layers of the structure; changing the number and identity of layers in the structure; and locating a layer of one conducting type nearer or farther from a substrateBenefits
These structures allow for locating precisely a superconducting layer for use in thin film superconducting devices such as SuFETs.Applications and Industries
Thin film superconducting devices and circuits.More Information
Gozar, et al., “High-temperature interface superconductivity between metallic and insulating copper oxides,” Nature, 455, 782-785 (2008). DOI:10.1038/nature07293Patents and Patent Applications
|Title and Abstract||
High temperature interfacial superconductivity
High-temperature superconductivity confined to nanometer-scale interfaces has been a long standing goal because of potential applications in electronic devices. The spontaneous formation of a superconducting interface in bilayers consisting of an insulator (La.sub.2CuO.sub.4) and a metal (La.sub.1-xSr.sub.xCuO.sub.4), neither of which is superconducting per se, is described. Depending upon the layering sequence of the bilayers, T.sub.c may be either .about.15 K or .about.30 K. This highly robust phenomenon is confined to within 2-3 nm around the interface. After exposing the bilayer to ozone, T.sub.c exceeds 50 K and this enhanced superconductivity is also shown to originate from a 1 to 2 unit cell thick interfacial layer. The results demonstrate that engineering artificial heterostructures provides a novel, unconventional way to fabricate stable, quasi two-dimensional high T.sub.c phases and to significantly enhance superconducting properties in other superconductors. The superconducting interface may be implemented, for example, in SIS tunnel junctions or a SuFET.
|Brookhaven National Laboratory||06/19/2012
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