Coherence and pairing enhancement in a trilayer cuprate with layer-selective charge order

Trilayer cuprates hold the record for the highest superconducting critical temperatures (T c), yet the underlying mechanism remains elusive. Using time- and angle-resolved photoemission spectroscopy (tr-ARPES), we uncover a striking interplay between charge order, superconducting gap magnitude, and quasiparticle coherence in Bi 2 Sr 2 Ca 2 Cu 3 O 10+δ (Bi2223). We present ARPES-based evidence of charge order on the inner CuO 2 plane -- as confirmed via resonant x-ray scattering (RXS) -- and show that the same inner plane hosts a large superconducting gap matching its doping, firmly establishing it as underdoped. Despite its underdoped nature, the inner plane also exhibits an exceptional degree of quasiparticle coherence; suppressing charge-order fluctuations further enhances this, making it comparable to that of the overdoped outer planes at elevated electronic temperatures. At the same time, on the overdoped outer planes we find larger superconducting gaps than what is seen on comparably doped single and bilayer cuprates, indicating an unexpected and simultaneous enhancement of both coherence and pairing interactions in Bi2223. These findings, supported by complementary single- and three-layer Hubbard model calculations, reveal a unique interlayer mechanism in which both pairing strength and phase coherence are optimized when interfacing planes with distinct hole concentrations, providing new microscopic insight into the record T c of Bi2223.