Quantum phenomena in unconventional superconductor junctions

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Symmetry of the Cooper pair can be generally classified into even-frequency spin-singlet even-parity (ESE) state, even-frequency spin-triplet odd-parity (ETO) state, odd-frequency spin-triplet even-parity (OTE) state and odd-frequency spin-singlet odd-parity (OSO) state. We present a general theory of the proximity effect in junctions between diffusive normal metals (DN) and unconventional superconductors in the framework of the Green's function formalism. Above four possible symmetry classes in a superconductor are considered: ESE, ETO, OTE and OSO state. For each of the above four cases symmetry and spectral properties of the induced pair amplitude in the DN are determined where only the even-parity s-wave pairing is possible due to the impurity scattering in DN. It is shown that the pair amplitude in a DN belongs respectively to an ESE, OTE, OTE and ESE pairing state In the presence of the Odd-frequency pairing state, the resulting density of state has a zero energy peak. The genera … More tion of the OTE state in the DN attached to the ETO p-wave superconductor is of particular interest in the relevance to the novel proximity effect in Sr2RuO4 junctions. In order to resolve this point, we are now preparing the junction made from Sr2RuO4 Using FIG technique. We further demonstrate that, quite generally, the spin-singlet even-parity (spin-triplet odd-parity) pair potential in a superconductor induces the odd-frequency pairing component with spin-singlet odd-parity (spin-triplet even-parity) near interfaces. The magnitude of the induced odd-frequency component is enhanced in the presence of the midgap Andreev resonant state due to the sign change of the anisotropic pair potential at the interface. We discussed the electronic Raman spectra of the quasi-two-dimensional spin-triplet superconductor Sr2RuO4. The Raman spectra are calculated using the Keldysh Green's function theory taking into account the order parameter collective mode. We take into account the effect of impurity scattering. The impurity scattering gives rise to considerable modification of the contribution from the quasiparticle excitations to the Raman spectra and simultaneously to the broadening of the collectivemode resonance peak and the shift of the peak position. Less