Reentrant $s$-wave superconductivity in the periodic Anderson model with attractive conduction band Hubbard interaction

Abstract

Spin-flip scattering from magnetic impurities has a strong pair-breaking effect in $s$-wave superconductors where increasing the concentration of impurities rapidly destroys superconductivity. For small Kondo temperature $T_K$ the destruction of superconductivity is preceded by the reentrant superconductivity at finite temperature range $T_{c2} < T < T_{c1}$, while the normal phase reappears at $T<T_{c2} \sim T_K$. Here we explore the superconducting phase in a periodic system modeled as the Anderson lattice with additional attractive on-site (Hubbard) interaction $g$ acting on the conduction band electrons. We solve the equations using dynamical mean field theory which incorporates Kondo physics, while the pairing interaction is treated on the static mean-field level. For large coupling $g$ we find reentrant superconductivity which resembles the case with diluted impurities. However, we find evidence that reentrant superconductivity is here not a consequence of many-body correlations leading to the Kondo effect, but it rather stems from a competition between the single-particle hybridization and superconducting pairing. An insight into the spectral functions with in-gap structures is obtained from an approximate noninteracting dual model whose solution interpolates between several exact limits.