Fractional power-law behavior and its origin in iron-chalcogenide and ruthenate superconductors: Insights from first-principles calculations

摘要

We perform realistic first-principles calculations of iron chalcogenides andruthenate based materials to identify experimental signatures of Hund'scoupling induced correlations in these systems. We find that FeTe andK$_x$Fe$_{2-y}$Se$_2$ display unusual orbital dependent fractional powerlawbehavior in their quasiparticle self energy and optical conductivity, aphenomena first identified in SrRuO$_3$. Strong incoherence in the paramagneticstate of these materials results in electronic states hidden to angle-resolvedphotoemission spectroscopy which reemerge at low temperatures. We identify theeffective low energy Hamiltonian describing these systems and show that theseanomalies are not controlled by the proximity to a quantum critical point butresult from coexistence of fast quantum mechanical orbital fluctuations andslow spin fluctuations.