Dynamical mean-field theory of a correlated gap formation in plutonium monochalcogenides

The correlated Kondo insulator state of the plutonium monochalcogenides is investigated using the dynamical mean-field theory (DMFT) in fluctuating-exchange approximation and the local-density $\text{approximation}+U$ $\left(\text{LDA}+U\right)$. The DMFT-dynamical fluctuations lead to a correlated insulator state at elevated temperature, in sharp contrast to the static $\text{LDA}+U$ approach that fails to reproduce both the insulating behavior and anomalous lattice constant. The DMFT conversely predicts the experimentally observed anomalous increase of the gap with pressure and explains the lattice constant very well.

Figure 1

(Color online) Top: the energy bands of PuTe computed with the $\text{LDA}+U$ method at the experimental lattice constant. Bottom: $\text{LDA}+\text{DMFT}$ quasiparticle band structure of PuTe at $T=600\text{K}$. The colors indicate the magnitude of the $k$-dependent spectral function, $-\frac{1}{\pi }\text{Im}G\left(\mathit{k},E\right)$.

Figure 2

(Color online) The $k$-integrated DOS calculated with the $\text{LDA}+\text{DMFT}\left(\text{FLEX}\right)$ method for (a) PuTe and (b) PuSe, for $U=3\text{eV}$. The experimental photoemission spectra (Refs. 15, 16) are given by the solid and dashed black lines.

Figure 3

(Color online) The relative total energy of PuTe versus lattice constant, calculated using the LDA, $\text{LDA}+U$ and $\text{LDA}+\text{DMFT}$ $\left(U=3\text{eV}\right)$ approaches. The experimental value is indicated by the vertical dashed line. Circles and crosses indicate metallic and insulator ground states, respectively.

Figure 4

(Color online) (a) Pressure dependence of the energy gap of PuTe. The blue (light gray) curve shows the experimental gap (Ref. 5) and the red (dark gray) curve depicts the $\text{LDA}+\text{DMFT}$ result $\left(U=3\text{eV}\right)$. (b) The quasiparticle bands around the chemical potential for two lattice constants, corresponding, respectively, to ambient pressure and $\sim 5.38\text{GPa}$.