Understanding the doping mechanisms in the simplest superconducting copper oxide—the infinite-layer compound ACuO2 (where A is an alkaline earth metal)—is an excellent way of investigating the pairing mechanism in high-transition-temperature (high-Tc) superconductors more generally1,2,3,4. Gate-induced modulation of the carrier concentration5,6,7 to obtain superconductivity is a powerful means of achieving such understanding: it minimizes the effects of potential scattering by impurities, and of structural modifications arising from chemical dopants. Here we report the transport properties of thin films of the infinite-layer compound CaCuO2 using field-effect doping. At high hole- and electron-doping levels, superconductivity is induced in the nominally insulating material. Maximum values of Tc of 89 K and 34 K are observed respectively for hole- and electron-type doping of around 0.15 charge carriers per CuO2. We can explore the whole doping diagram of the CuO2 plane while changing only a single electric parameter, the gate voltage.
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Schön, J., Dorget, M., Beuran, F. et al. Superconductivity in CaCuO2 as a result of field-effect doping. Nature 414, 434–436 (2001). https://doi.org/10.1038/35106539
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