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Description
Layered Ruddlesden–Popper halide perovskites are an attractive platform for investigating excited-state many-body physics, since quantum and dielectric confinement, strong spin–orbit coupling, and pronounced lattice dynamics can coexist and interplay in this material family.
Here, we present angle-resolved and time-resolved photoelectron spectroscopy measurements on single crystals of (BA)₂(MA)₂Pb₃I₁₀. We directly probe the valence-band dispersion and follow the evolution of photoexcited carriers after 3.1 eV excitation. The measured photoemission intensity maps are in good agreement with first-principles band-structure calculations and yield bare effective masses of −0.18 ± 0.02 mₑ for holes and 0.12 ± 0.02 mₑ for electrons. After photoexcitation, hot carriers relax to the conduction-band minimum on a sub-picosecond timescale and subsequently evolve into bound electron–hole pairs. Their momentum distribution is consistent with a Wannier exciton with a Bohr radius of 2.8 nm, while no evidence of self-trapping into small polarons is observed within 120 ps after excitation. In parallel, no resolvable spin–orbit splitting is detected in the photoexcited conduction band, placing an upper bound of αC < 2.5 eVÅ on the photoinduced Rashba coupling.