Spatial inhomogeneity and strong correlation physics: A dynamical mean-field study of a model Mott-insulator–band-insulator heterostructure

We use the dynamical mean-field method to investigate electronic properties of heterostructures in which a finite number of Mott-insulator layers are embedded in a spatially infinite band insulator. The evolution of the correlation effects with the number of Mott insulating layers and with position in the heterostructure is determined, and the optical conductivity is computed. It is shown that the heterostructures are generally metallic, with moderately renormalized bands of quasiparticles appearing at the interface between the correlated and uncorrelated regions.

Figure 1

Layer-resolved spectral function calculated for 10-layer heterostructure for $U=16t$, $\epsilon =15$. The heterostructure is defined by $+1$ charges placed at $z=\pm 0.5,\pm 1.5,\dots \pm 4.5$ so the electronic $\left(B\right)$ sites are at integer values of $z$.

Figure 2

Total charge density (open squares) and charge density from the coherent part near the Fermi level (open circles). For comparison, the total charge density calculated by applying the Hartree-Fock approximation to the Hamiltonian is shown as filled symbols. The parameters are the same as in Fig. 1.

Figure 3

(a) Dispersion relations of filled-subband quasiparticles calculated for three-layer heterostructure with $U=16t$ and $\epsilon =15$. The solid and broken lines are for odd and even $\alpha$, respectively. (b) Subband quasiparticle weights. (c,d) Quasiparticle wave functions for $\alpha =1,3,5$ and 2,4 at $\omega =0$. Here the heterostructure is defined by $+1$ charges placed at $z=0,\pm 1$ so the electronic $\left(B\right)$ sites are at half integer values of $z$.

Figure 4

Heavy lines: low-frequency (quasiparticle-region) optical conductivity for $n=3$, $U=16t$ heterostructure. Peaks arise from transition among subbands shown in Fig. 3a. Light lines: conductivity calculated from Hartree-Fock approximation to same Hamiltonian.