The thermoelectric coefficient η(T ) in unconventional superconductors is enhanced below Tc by intermediate strength impurity scattering that is intrinsically particle-hole asymmetric. We compute η(T ) for a strong-coupling d-wave superconductor and investigate the effects of inelastic scattering originating from electron-boson interactions. We show that η(T ) is severely suppressed at temperat...

We study a Hubbard model with a strong onsite impurity potential based on an improved fluctuation-exchange (FLEX) approximation, which we call the GV I -FLEX method. We find that (i) both local and staggered susceptibilities are strongly enhanced around the impurity. By this reason, (ii) the quasiparticle lifetime as well as the local density of states (DOS) are strongly suppressed in a wide ar...

The NLSE soliton scattering by impurities is considered in the framework of the one-dimensional model. The scattering intensity is characterized by the reflection coefficient. The reflection coefficient of the soliton is calculated in the Born approximation of the perturbation theory for the following cases: (i) and isolated impurity, (ii) two point impurities, and (iii) a regular or random sys...

We review the progress of nonmagnetic impurity doping studies on Fe-based superconductors. On the theoretical side, two highly promising candidates for the pairing symmetry order parameter, i.e. the multi-gap s++ and s± wave models, have been proposed but continuously debated. The debate arises because of the complex gap structure and exceptional magnetic and metallic behaviors of Fe-based supe...

A microscopic theory of the plasma resonance in layered metals is presented. It is shown that electron-impurity scattering can suppress the plasma resonance in the normal state and sharpen it in the superconducting state.

We investigate factorized scattering from a reflecting and transmitting impurity. Bulk scattering is non trivial, provided that the bulk scattering matrix depends separately on the spectral parameters of the colliding particles, and not only on their difference. We show that a specific extension of a boundary algebra encodes the underlying scattering theory. The total scattering operator is con...

Quantum impurity problems occur in various areas of physics. Some examples are: an impurity spin in a metal (the Kondo problem), the two-impurity Kondo problem, a defect or impurity spin in a spin chain, tunnelling through a barrier in a quantum wire proton-monopole scattering (the Callan-Rubakov effect). Some common features of these problems are: 1. gapless “bulk” excitations (ie. far from th...