Revisiting the origin of satellites in core-level photoemission of transparent conducting oxides: The case of $n$-doped ${\mathrm{SnO}}_2$

The longstanding problem of interpretation of satellite structures in core-level photoemission spectra of metallic systems with a low density of conduction electrons is addressed using the specific example of Sb-doped ${\mathrm{SnO}}_2$. Comparison of ab initio many-body calculations with experimental hard x-ray photoemission spectra of the Sn $4d$ states shows that strong satellites are produced by coupling of the Sn core hole to the plasma oscillations of the free electrons introduced by doping. Within the same theoretical framework, spectral changes of the valence band spectra are also related to dynamical screening effects. These results demonstrate that, for the interpretation of electron correlation features in the core-level photoelectron spectra of such narrow-band materials, going beyond the homogeneous electron gas electron-plasmon coupling model is essential.

Figure 1

(a) Scheme of the final-state configurations for the (S)creened and (U)nscreened channels according to the Kotani-Toyazawa models [20, 22]. (b)–(d) Core-level HAXPES spectra of O $1s$, Sn $3d_{5/2}$, and Sn $4d$ for nominally undoped ${\mathrm{SnO}}_2$ (bottom) and Sb-doped ${\mathrm{SnO}}_2$ (top), respectively. The background of the spectra has been subtracted using a Shirley profile.

Figure 2

(Top) GW+C spectral function for the Sn $4d$ region of undoped (black) and doped (blue, red) compounds, the latter corresponding to two different carrier concentrations. (Bottom) Quasiparticle (QP) contribution. Inset: loss function calculated for the same carrier concentrations.

Figure 3

Comparison of HAXPES Sn $4d$ spectra (bottom) and $d$-orbital projection ($d$-PSF) of the spectral functions (top) for undoped and doped ${\mathrm{SnO}}_2$. All curves are aligned to the position of the experimental Sn $4d_{5/2}$ term.

Figure 4

(a) GW+C spectral functions whose angular-projected contributions have been weighted by the respective photoionization cross sections [50]. (b) HAXPES VB spectra normalized to the maximum intensity of the stronger features. The spectral contribution of the conduction states for the doped sample has been enhanced by a factor 20.