Fig. 1
From: Signatures of Mottness and Hundness in archetypal correlated metals
Schematic sketch of the behavior of four characteristic temperature scales. \(T_{{\mathrm{orb}}}^{{\mathrm{onset}}}\) (green dashed), \(T_{{\mathrm{spin}}}^{{\mathrm{onset}}}\) (green solid), \(T_{{\mathrm{orb}}}^{{\mathrm{cmp}}}\) (red dashed), \(T_{{\mathrm{spin}}}^{{\mathrm{cmp}}}\) (red solid) mark the onset and the completion of screening of orbital and spin degrees of freedom, respectively, as functions of the bare gap, Δb = U − 2J, between the upper and lower Hubbard side band. White (gray) background indicates Hund (Mott) behavior at small (large) Δb. A crossover between both (oblique gray lines) is found at intermediate Δb. Open symbols on the left give the values of these scales as obtained from DMFT + NRG calculations for our three-band Hubbard–Hund model, with J = 1 and U = 3 (green), U = 5.5 (gray), and U = 6.5 (yellow). On the right, closed symbols give corresponding values obtained from DFT + DMFT calculations for the materials Sr2RuO4 (green) and V2O3 (yellow). Left: cartoon of two-stage screening for three local levels with J ≠ 0, containing two electrons with total spin S = 1: with decreasing temperature, first orbital screening of the hole occurs, whereby a delocalized spin 1/2 combines with the local spin 1 to yield an orbital singlet with spin 3/2; then spin screening occurs, yielding an orbital and spin singlet10. The energy scales characterizing the two screening stages lie far apart for Hund systems, but close together for Mott systems. Insets: cartoons of the local density of states, A(ω), for a Hund system (left) and a Mott system close to the Mott transition (right), summarizing the essential differences in the evolution of the quasiparticle peak with decreasing temperature (purple to yellow to blue)
