Marco Monni

Fully Band-Resolved Scattering Rate in MgB2 Revealed by the Nonlinear Hall Effect and Magnetoresistance Measurements

We have measured the normal state temperature dependence of the Hall effect and magnetoresistance in epitaxial MgB2 thin films with variable disorders characterized by the residual resistance ratio RRR ranging from 4.0 to 33.3. A strong nonlinearity of the Hall effect and magnetoresistance have been found in clean samples, and they decrease gradually with the increase of disorders or temperature. By fitting the data to the theoretical model based on the Boltzmann equation and ab initio calculations for a four-band system, for the first time, we derived the scattering rates of these four bands at different temperatures and magnitude of disorders. Our method provides a unique way to derive these important parameters in multiband systems.

Intraband vs. interband scattering rate effects in neutron irradiated MgB2

One of the most important predictions of the two-gap theory of superconductivity concerns the role of interband scattering (IBS) by impurities. IBS is expected to decrease the critical temperature, Tc, of MgB2 to a saturation value of about 20 K, where the two gaps merge to a single one. These predictions have been partially contradicted by experiments. In fact, Tc does not saturate in irradiated samples, but decreases linearly with residual resistivity and the merging of the gaps has been observed at a much lower Tc (11 K). In this paper we argue that, while at low level of disorder IBS is the leading mechanism that suppresses superconductivity, at higher disorder the experimental results can only be understood if the smearing of the density of states due to intraband electron lifetime effects is considered.

Isoelectronic Ru substitution at the iron site in SmFe 1 − x Ru x AsO 0.85 F 0.15 and its effects on structural, superconducting, and normal-state properties

In this work we present a systematic experimental and theoretical study of the structural, transport, and superconducting properties of

Multiband conductivity and a multigap superconducting phase in V3Si films from optical measurements at terahertz frequencies

\text{Sm}({\text{Fe}}_{1\ensuremath{-}x}{\text{Ru}}_{x})\text{As}({\text{O}}_{0.85}{\text{F}}_{0.15})

Magnetoresistivity as a probe of disorder in the it and σ bands of MgB2

polycrystalline samples as a function of Ru content

Theoretical investigation of FeTe magnetic ordering under hydrostatic pressure

(x)

The role of Coulomb interaction in the superconducting properties of CaC6 and H under pressure

ranging from 0 to 1. The choice of Ru as isoelectronic substitution at Fe site of F-doped compounds allows to better clarify the role of structural disorder in modifying the normal and superconducting properties of these recently discovered multiband superconductors. Two different regions are identified: the Fe-rich phase

Phononic self-energy effects and superconductivity in CaC6

(xl0.5)

Multiband superconductivity in Pb, H under pressure and CaBeSi from ab initio calculations

where superconducting and normal-state properties are strongly affected by disorder induced by Ru substitution; the Ru-rich phase

Probing the electron-phonon coupling in MgB2 through magnetoresistance measurements in neutron irradiated thin films

(xg0.5)