Fig. 3: Spectral weight transfer and breakdown of the orbital-selective Mott phase (OSMP) upon K deposition.

Normalised T-dependent energy distribution curves (EDCs) (top), symmetrised EDCs (middle) and after subtraction of the 40 K data (bottom) for x = a 0.5 and b 0.2. The EDCs are extracted from a region near the S-point, integrated over 0.6 ≤ k_x ≤ 0.8 (for the raw data, see Supplementary Fig. 2). c The symmetrised EDCs of T = 6, 40 K in b (top) and their difference (bottom). The ‘dip’ and ‘hump’ are defined as the area in 0 ≤ BE(eV) ≤ 0.2 and 0.2 ≤ BE(eV) ≤ 0.8 regions, respectively. d T-dependent areas of the ‘dip’ and ‘hump’. e–g ARPES images (right) and corresponding 2D curvature plots⁵⁰ (left) along S-Γ₁-S for x = e 0.5, f 0.2, and g x = 0.2 with an electron doping value of 0.02 measured at T = 10 K using σ-polarised light. Solid white/black/red guidelines indicate the dispersions of α-/β-/γ-bands, respectively (Supplementary Fig. 7). For g, 0.2 monolayer of K coverage was deposited in situ on the surface of Ca_2-xSr_xRuO₄ (x = 0.2) to achieve electron doping effect lightly (about 0.02 electrons, Supplementary Fig. 8) h Schematic illustration of alkali metal (potassium K) deposition on the surface of a Ca_2-xSr_xRuO₄ (x = 0.2) single crystal.