Figure 3. Observation of Fröhlich polaron spectra by ARPES at SrTiO₃ surface prepared at 700 °C.

(a) Symmetrized Fermi surface of SrTiO₃ in k_x−k_y space. Γ₁₀=2π/a(1, 0)∼(1.61, 0) Å⁻¹. (b) Dispersion from Γ₁₁ along [11] direction with d_xy orbital character. Dispersion from Γ₁₀ along [01] direction with d_xz orbital character is shown in f. The momentum cuts are shown in dashed while lines. (c) Energy-second-derivative image of spectra in b. (d) Simulated large polaron dispersions with d_xy/d_yz and d_xz orbital characters. (e) Constant-energy contours of large polaron electronic structure, characterized by two (or more) similar electron pockets, indicated by dashed lines. (g) EDC stacks of spectra in b. Black empty circles indicate the EDC shown in h. (h) Franck–Condon line shape fitting. The fitted EDC (red line) is composed of three Gaussian peaks (blue line), separated in energy by 90 meV, and a hump-like background (red dashed line). Black dashed lines in b,c and f are fitted dispersions for the zero-order bands. See Supplementary Fig. 2 for details.