A second hump in a superconducting dome

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Science  20 Jun 2014:
Vol. 344, Issue 6190, pp. 1355
DOI: 10.1126/science.344.6190.1355-f

Pure strontium titanate (SrTiO3) does not conduct electricity, but adding tiny amounts of impurities can turn it into a perfect conductor: a superconductor. Lin et al. found that, for a particular concentration of extra electrons introduced by adding Nb to the samples, the temperature at which SrTiO3 becomes superconducting (Tc) has a maximum. This concentration coincides with the state when the electrons have filled up one energy band of the material and are just starting to fill up another. By measuring the electrical resistivity of the samples, they found that the overall shape of the Tc dependence on the electron concentration was a two-humped dome. Unlike superconducting domes in other materials, the base of the dome was quite broad and spanned a range of over three orders of magnitude of carrier concentration.

Phys. Rev. Let. 112, 207002 (2014).

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