Spectral Density and Metal-Insulator Phase Transition in Mott Insulators within Reduced Density Matrix Functional Theory

We present a method for calculating the spectrum of periodic solids within reduced density matrix functional theory. This method is validated by a detailed comparison of the angular momentum projected spectral density with that of well-established many-body techniques, finding very good agreement in all cases. The physics behind the pressure induced insulator-metal phase transition in MnO is investigated. The driving mechanism of this transition is identified as increased crystal field splitting with pressure, resulting in a charge redistribution between the Mn $e_g$ and $t_{2}g$ symmetry projected states.

Figure 1

Density of states for the TMOs in the presence of antiferromagnetic order. Site and angular momentum projected spectral density are also presented for transition metal $e_g$ and $t_{2g}$ states and oxygen-$p$ states. In addition, XPS and BIS spectra (shifted up for clarity) are presented for comparison [22, 23, 24, 25, 26]. Again, $\alpha =0.656$ for all materials.

Figure 2

Left panel: on-site magnetic moment (in ${\mu }_B$) for MnO as a function of reduced volume ($v/v_0$). Right panel: Mn $d$-band occupancy resolved into $e_g$ and $t_{2g}$ components.

Figure 3

$t_{2g}$ (right panel) and $e_g$ (left panel) projected spectral density for MnO as a function of energy (in eV) and reduced volume. Results are obtained using RDMFT. Spectral density for different reduced volumes are shifted vertically for clarity.