Seminar: Unconventional superconductivity and its possible realization

Unconventional superconductivity may be defined as the electronic pairing induced breaking of symmetries beyond the U(1) symmetry. A hallmark for the unconventional superconductivity is the non-s-wave orbital part of the superconducting order parameter (OP). Sr2RuO4 and UTe2, for which a non-s-wave pairing is quite well established, are two promising candidates for the more exotic odd-party, spin-triplet superconductivity. While Sr2RuO4 is the first and only layered perovskite superconductor with the normal electronic states on the Fermi surface evolving primarily from 4d orbitals, UTe2 is a (recently discovered) heavy fermion superconductor possessing a highly anisotropic Fermi surface with electronic states dominated by strongly correlated 5f electrons of U. Both Sr2RuO4 and UTe2 are furthermore promising candidates for the spin-fluctuation-mediated pairing established originally in superfluid 3He. In this talk I will give a brief overview of the experimental work on Sr2RuO4 and UTe2 that is most relevant to the unconventional nature of superconductivity including our own work on the phase-sensitive determination of the symmetry properties of the OP of these two superconductors.