Superconductivity in CaCuO2 as a result of field-effect doping

Understanding the doping mechanisms in the simplest superconducting copper oxide-the infinite-layer compound ACuO(2) (where A is an alkaline earth met al)Dis an excellent way of investigating the pairing mechanism in high-tran sition-temperature (high-T-c) superconductors more generally(1-4). Gate-ind uced modulation of the carrier concentration(5-7) to obtain superconductivi ty is a powerful means of achieving such understanding: it minimizes the ef fects of potential scattering by impurities, and of structural modification s 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 T-c 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 C uO2 plane while changing only a single electric parameter, the gate voltage .