Coexistence of high-T_c superconductivity and ferro- or antiferroelectricity in YBa₂Cu₃O_7-δ

Abstract

We report on pronounced anomalies of the absorption and dispersion of the sound-induced rf magnetic field in YBa₂Cu₃O_7-δ. The experimental findings are highly indicative of a near-coincidence of the superconducting transition and an antiferrodistortive transition into either an antiferroelectric or improper ferroelectric state. To our knowledge the experimental technique presented here, so far is the only method which offers the possibility to show experimentally that both superconductivity and ferro-/antiferroelectricity may coexist. Furthermore, it is demonstrated that in YBa₂Cu₃O_7-δ microtwinning plays an important role for the dielectric phase transition to become manifest. The possible relationship between our findings and high-T_c superconductivity is also discussed.