Why Broken Time Reversal Symmetry Occurs in Unconventional Superconductors?
Manfred Sigrist, Yukawa Institute for Theoretical Physics, Kyoto University, Kyoto 606-8502, Japan Presenting Author: M. Sigrist In recent years a number of superconductors have been found which very likely realize phases with broken time reversal symmetry T. They are identified by their magnetic properties, for example in m SR experiments. Two well-known examples amoung the heavy Fermion superconductors are U1-xThxBe13 and UPt3 which both exhibit superconducting double transitions. Below the second phase transition T-violation occurs. It can be shown that among all instabilities possible within an unconventional superconducting a T-violating one is most favored by the gain of condensation energy. This is not only true for second transitions in the bulk but also at surfaces and interfaces, as probably observed in high-temperature superconductors. In contrast, in Sr2RuO4 a T-violating phase occurs immediately at the onset of superconductivity. We will show that in this quasi-two-dimensi
