Unusual pressure-induced metallic state in the correlated narrow band-gap semiconductor FeSi

Abstract

The extent of electron correlations in FeSi and Fe-3$d$/Si-3$p$ hybridization embeds a narrow gap in the resultant quasiparticle peak at the Fermi level. Here, the authors investigate the effect of compression tuning of this electronic fine structure and demonstrate its sensitivity to lattice heterogeneities, e.g., those resulting from extrinsic lattice strains. Pressurization tunes the mobility edge relative to the Fermi level until an unusual metallic state ensues beyond about 15 GPa, which does not involve any structural instability of the original $B$20-type cubic structure.