Extended Data Fig. 3: Undoped sample versus electron-doped sample (forbidden optical absorption) on near-resonance pumping.

a, Schematic illustration of the electronic structure of undoped black phosphorus with unoccupied CB. Direct optical transition from VB to CB is allowed on near-resonance pumping. b,c, TrARPES dispersion images measured in undoped sample along the AC direction at Δt = −1 ps (b) and Δt = 0 (c). The pump beam is polarized along the AC direction with photon energy of 380 meV and the pump fluence is 0.7 mJ cm⁻². d,e, Second-derivative image and EDCs of TrARPES data shown in c. f, Extracted dispersions before pump (dashed black curve) and with pump (red curves). g, Schematic illustration of the electronic structure of electron-doped black phosphorus with occupied CB edge. Direct optical transition from VB to CB is forbidden on near-resonance pumping. h–l, Similar results as b–f but in electron-doped sample using pump pulses with photon energy of 400 meV and pump fluence of 3 mJ cm⁻². The Fermi energy is obtained by the Fermi–Dirac fitting to the spectrum of electron-doped black phosphorus before pump (Δt = −1 ps).