There are two possible spin states of Cooper pair responsible for the superconducting state, the spin-singlet and spin-triplet states, but most superconductors have singlet states with no spin degrees of freedom.
There has been accumulating evidence that Sr_2RuO_4 is one of the most promising candidates for spin-triplet superconductors.
Moreover, a chiral superconducting state, in which the time reversal symmetry is spontaneously broken, is believed to be realized in this oxide.
In recent years, it has been uncovered that such chiral spin-triplet superconductivity has an aspect as a "topological superconductor", showing superconducting topological quantum phenomena.
Furthermore, the Mott insulator Ca_2RuO_4, with Sr replaced by Ca, also shows superconductivity under pressure.
We aim to discover and understand topological quantum phenomena peculiar to superconductors broken in time reversal symmetry, through experiments on bulk superconducting properties of Sr_2RuO_4, superconducting devices using Sr_2RuO_4, and external field effects such as pressure and electric field to Ca_2RuO_4.
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