Enhanced coherence and layer-selective charge order in a trilayer cuprate superconductor

TL;DR

This study uses advanced spectroscopy to reveal how charge order and layer-specific doping influence superconductivity in a trilayer cuprate, offering insights into its record high critical temperature.

Contribution

It provides the first ARPES evidence of charge order on the inner CuO2 plane and shows how interlayer interactions optimize superconductivity in trilayer cuprates.

Findings

Charge order is present on the inner CuO2 plane.

The inner plane has a larger superconducting gap despite being underdoped.

Quasiparticle coherence is enhanced by suppressing charge-order fluctuations.

Abstract

Trilayer cuprates hold the record for the highest superconducting critical temperatures ($T_{\text{c}}$), 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$_{10+\delta}$ (Bi2223). This constitutes ARPES-based evidence of charge order on the inner CuO$_2$ plane, as confirmed via resonant x-ray scattering (RXS); in addition, the same inner plane hosts a superconducting gap significantly larger than that of the overdoped outer planes, firmly establishing it as underdoped. Unexpectedly, 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. These findings, supported by complementary three-layer single-band Hubbard 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 $T_{\text{c}}$ of Bi2223.