Quasiparticles at the Mott Transition in ${\mathrm{V}}_2{\mathrm{O}}_3$: Wave Vector Dependence and Surface Attenuation

We present an angle resolved photoemission study of ${\mathrm{V}}_2{\mathrm{O}}_3$, a prototype system for the observation of Mott transitions in correlated materials. We show that the spectral features corresponding to the quasiparticle peak in the metallic phase present a marked wave vector dependence, with a stronger intensity along the $\Gamma Z$ direction. The analysis of their intensity for different probing depths shows the existence of a characteristic length scale for the attenuation of coherent electronic excitations at the surface. This length scale, which is larger than the thickness of the surface region as normally defined for noncorrelated electronic states, is found to increase when approaching the Mott transition. These results are in agreement with the behavior of quasiparticles at surfaces as predicted by Borghi et al. [Phys. Rev. Lett. 102, 066806 (2009)].

Figure 1

(a) Normal emission photoelectron spectra taken at 300 K (PI) and 200 K (PM) from the (001) surface of $({\mathrm{V}}_{0.989}{\mathrm{Cr}}_{0.011}{)}_2{\mathrm{O}}_3$. (b) Spectra taken at 300 K (PM) from the (001) surface of ${\mathrm{V}}_2{\mathrm{O}}_3$ at normal (0°) and grazing (60° from normal) photoelectron emission angle.

Figure 2

Angular dependence of the background subtracted photoemission yield at $h\nu =9\mathrm{eV}$ [from normal to grazing emission corresponds to spectra from red to violet, i.e., from bottom to top in (a) and from top to bottom in (b)–(d)]; the top spectra always correspond to emission from $\Gamma Z$.

Figure 3

Angular attenuation of the quasiparticle weight. The data points correspond to the spectra in Figs. 2b, 2c, 2d. The curves were normalized to their values at normal emission.