Correlated excited states in the narrow band gap semiconductor FeSi and antiferromagnetic screening of local spin moments

摘要: The physical properties of the semiconductor FeSi with very narrow band gap, anomalous behavior magnetic susceptibility and metal-insulator transition at elevated temperatures attract great interest due to still controversial theoretical understanding their origin. On one side purely bandlike mechanism gap formation in low temperature is well established; on other a number experiments interpretation suggest rich physics strong correlations finite temperature. In this work we use an ab initio scheme based random-phase approximation local spin-density (RPA@LSDA) reveal role electron correlation effects extending it by applying fixed spin moment constraint. parameter-free framework show that essentially alter one-electron LSDA results leading additional state Fe, whose energy almost degenerate nonmagnetic ground state. This explains high-field experiments, which found first-order metamagnetic phase into metallic ferromagnetic Our strongly correlated nature low-energy excitations FeSi. From our supercells calculations these are exhibit Kondo-like since antiferromagnetic screening present.