Structural phase transitions, ferroelectricity and high temperature superconductivity

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Abstract
Calculations based on a local double well potential show the near coincidence of a ferroelectric transition and a high temperature superconducting phase transition. Using double well parameters consistent with the Abrahams-Kurtz-Jamieson (AKJ) relation for ferroelectric phase transitions in oxide perovskite ferroelectrics we find that the superconducting transition temperature falls above or below the ferroelectrics transition temperature depending on modest changes in the height of the unrenormalized double well barrier. For the ReBa2Cu3O7-δ superconductors, this ferroelectric transition appears to fall above the superconducting transition temperature. The shallowness of the double-well in this case is consistent with our previous suggestion that the ReBa2Cu3O7-δ are relaxor ferroelectrics with a ferroelectric transition temperature that depends on the specific rare earth and a more or less constant superconducting transition temperature in the 90–100°K region. This result has important implications for the processing and statility of the perovskite oxides for superconducting device applications. A possible connection between these results and various theoretical models of superconductivity is discussed.