Superconducting Double Transition and the Upper Critical Field Limit of Sr2RuO4 in Parallel Magnetic Fields

摘要

We studied the specific heat and thermal conductivity of the spin-tripletsuperconductor Sr2RuO4 at low temperatures and under oriented magnetic fieldsH. We resolved a double peak structure of the superconducting transition undermagnetic field for the first time, which provides thermodynamic evidence forthe existence of multiple superconducting phases. We also found a clearlimiting of the upper critical field Hc2 for the field direction parallel tothe RuO2 plane only within 2 degrees. The limiting of Hc2 occurs in the sameH-T domain of the second superconducting phase; we suggest that the twophenomena have the same physical origin.