Electronic correlations in FeSb$_2$: a QSGW+DMFT investigation

Optical conductivity measurements of iron antimonide (FeSb$_2$) have shown that a large spectral weight redistribution takes place when the material is cooled down to 10 K [1]. On the theoretical side, density functional theory and GW calculations are known to predict metallic and insulating phases with a too large band gap, respectively. These findings suggest that electron correlations are relevant for the gap formation in FeSb$_2$ and that a theoretical description beyond a many-body perturbation theory is required. In this study we investigate from an \textit{ab initio} perspective the role played by electron correlations on the electronic properties of FeSb$_2$. With our combined quasiparticle self-consistent GW (QSGW) and dynamical mean field theory (DMFT) calculations we reveal that many-body correlation effects lead to a temperature dependent gap renormalization. In particular, our calculations indicate that the dynamical behavior of the real parts of valence and conduction self-energies is of great importance to the gap formation in FeSb$_2$. [1] Phys. Rev. B {\bf 82}, 245205 (2010).