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We study the emergence of triplet superconductivity in an electronic system near a ferromagnetic quantum critical point (FQCP). Previous studies found that the superconducting transition is of second order, and is strongly reduced near the FQCP due to pair-breaking effects from thermal spin fluctuations. In contrast, we show that near the FQCP, the system avoids pair-breaking by undergoing a transition at a much larger . At some distance from the FQCP, a second order superconducting transition emerges at a tricritical point.

Since the discovery of high cuprates, superconductivity has been sought in nickel or cobalt oxides, because the elements are neighboring to copper in the periodic table; however the attempts were in vain. We found the first superconductor, NaCoOHO ( ≈ 0.35, ≈ 1.3), in cobalt oxides.

Motivated by the recent discovery of superconductivity in the cobalt oxide superconductors, we calculate the upper critical field for the CoO layer. Using the lattice version of the Gor’kov equations we investigate how applied magnetic field affects superconductivity on a triangular lattice. We demonstrate the possibility of field-induced transition from singlet to triplet superconductivity, explaining the observed temperature dependence of the upper critical field.

The strength and effect of Coulomb correlations in the (superconducting when hydrated) ≈ 1/3 regime of NaCoO have been evaluated using the correlated band theory LDA+U method. Our results, neglecting quantum fluctuations, are: (1) there is a critical = 3 eV, above which charge ordering occurs at = 1/3, (2) in this charge-ordered state, antiferromagnetic coupling is favored over ferromagnetic, while below , ferromagnetism is favored; and (3) carrier conduction behavior should be very asymmetric for dopings away from = 1/3. For < 1/3, correlated hopping of parallel spin pairs is favored, suggesting a triplet superconducting phase.

The scattering process responsible for connecting the bands remains one of the last open questions on the physical properties of MgB. Through the analysis of the equilibrium and photo-induced far-infrared properties as well as electron spin resonance of MgB we propose a phonon mediated energy transfer process between the bands based on the coupling of quasiparticles to an phonon.

In strong-coupling superconductors with a short electron mean free path the self-energy effects in the superconducting order parameter play a major role in the phonon manifestation of the point-contact spectra at above-gap energies. We compare the expressions for the nonlinear conductivity of tunnel, ballistic, and diffusive point-contacts and show that these expression are similar and correspond to the measurements of the phonon structure in the point-contact spectra for the π-band of MgB.

Quantum chemical calculations at molecular mechanical level were carried out to search a possible correlation between the number of pyrrole units and the total energy, dipole moment and dihedral angles of the possible polymers of pyrrole molecule. The ideal superconductive polymer of that molecule could be formed by repeating asymmetric type of dimer up to 3 units.