Orbital-selective Mottness Driven by Geometric Frustration of Interorbital Hybridization in Pr4Ni3O10

The interplay among orbital-selective Mott physics, Hund's coupling, tunable structural motifs, and Kondo-like scattering establishes a compelling paradigm for understanding and engineering correlated multi-orbital systems, as vividly exemplified by nickelate superconductors. Here, using high-resolution angle-resolved photoemission spectroscopy combined with theoretical calculations, we systematically investigate the electronic properties of trilayer nickelates. In La4Ni3O10, we observe pronounced interorbital hybridization, whereas in Pr4Ni3O10, the flat d_(z^2 ) band becomes markedly incoherent and diminishes in spectral weight. By contrast, the dispersive d_(x^2-y^2 ) bands retain coherence in both compounds. This striking incoherence/coherence dichotomy identifies an orbital-selective Mott phase modulated by the interlayer Ni-O-Ni bonding angle. The depletion of the d_(z^2 ) orbitals further frustrates the interorbital hybridization and influences the density-wave transition in Pr4Ni3O10. Moreover, the density-wave gap is substantially reduced in Pr4Ni3O10, likely due to extra scattering channels provided by the local moments of Pr3+ cations. Our findings elucidate the intricate interplay among lattice, orbital, spin, and electronic degrees of freedom and reveal a feasible structural control parameter for the multi-orbital correlated state in trilayer nickelates, which provide a concrete framework for understanding the emergence of superconductivity under high pressure.