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High-temperature superconductivity is a historical name for superconductivity above earlier metallic benchmarks. The original Bednorz-Müller experiment operated at tens of kelvins, requiring deep cooling; cuprate superconductors opened a new materials family.^[ref]

A higher superconducting transition temperature enlarges the available operating range, but useful transport also needs a sufficient superconducting critical current at the operating temperature and magnetic field. In a ceramic, connections between grains can limit the whole specimen even when individual grains support superconductivity. This connects the materials problem to superconducting weak links and the Josephson effect. The parallel-path model of a superconducting ceramic below isolates why connectivity matters.

A physicist whose work addresses high-temperature superconductivity and the pseudogap. His 2005 perspective with colleagues examines why a depletion of low-energy electronic states can appear above the temperature where superconductivity begins. Determining whether this behavior assists pairing, competes with it, or signals a distinct phase is essential to interpreting the normal state from which superconductivity develops. The article presents these alternatives as unresolved physical questions.^[ref]