Surface Dead Layer for Quasiparticles Near a Mott Transition

Electron quasiparticles are progressively weakened by correlations upon approaching a continuos Mott metal-insulator transition in a bulk solid. We show that corresponding to the bulk weakening, a dead layer forms below the surface of the solid, where quasiparticles are exponentially suppressed. The surface dead layer depth is a bulk property and diverges when the Mott transition is approached. We describe this phenomenon in a Hubbard model within a self-consistent Gutzwiller approximation. The photoemission data of Rodolakis et al. [Phys. Rev. Lett. 102, 066805 (2009)] in ${\mathrm{V}}_2{\mathrm{O}}_3$ appear to be in accord with this physical picture.

Figure 1

The quasiparticle weight $Z(z)=R^2(z)$ as a function of the coordinate $z$ perpendicular to the surface (in units of the lattice spacing) for a 100-layer slab. The interaction parameter at $z=0$ is $U_s=20t$, while the bulk $U$ is $15.98t$ in the upper panel and $15t$ in the lower one (while $U_c=16$). The insets show the behavior of $Z$ close to the two surfaces, the highest curve corresponding to the bulklike surface, the other to $U_s=20t$.

Figure 2

Quasiparticle weight dependence on the distance $z$ from the surface for two different bulk $U$ values and for two cases: one where only the first layer has $U_s=20t>U$ (upper curve in each panel), the other where five surface layers have $U_s=20t$.

Figure 3

Log scale plot of $R_{\mathrm{bulk}}-R(z)$ versus $z$ for $U=15.99$, $U_s=20t$ and for different thicknesses of the slab $N=60,100,200,400$.