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Evolution from a charge-ordered insulator to a high-temperature superconductor in Bi 2 Sr 2 (Ca,Dy)Cu 2 O 8+δ .

Changwei ZouJaewon ChoiQizhi LiShusen YeChaohui YinMirian Garcia-FernandezStefano AgrestiniQingzheng QiuXinqiang CaiQian XiaoXingjiang ZhouKe-Jin ZhouYayu WangYing Ying Peng
Published in: Nature communications (2024)
How Cooper pairs form and condense has been the main challenge in the physics of copper-oxide high-temperature superconductors. Great efforts have been made in the 'underdoped' region of the phase diagram, through doping a Mott insulator or cooling a strange metal. However, there is still no consensus on how superconductivity emerges when electron-electron correlations dominate and the Fermi surface is missing. To address this issue, here we carry out high-resolution resonant inelastic X-ray scattering and scanning tunneling microscopy studies on prototype cuprates Bi 2 Sr 2 Ca 0.6 Dy 0.4 Cu 2 O 8+δ near the onset of superconductivity, combining bulk and surface, momentum- and real-space information. We show that an incipient charge order exists in the antiferromagnetic regime down to 0.04 holes per CuO 2 unit, entangled with a particle-hole asymmetric pseudogap. The charge order induces an intensity anomaly in the bond-buckling phonon branch, which exhibits an abrupt increase once the system enters the superconducting dome. Our results suggest that the Cooper pairs grow out of a charge-ordered insulating state, and then condense accompanied by an enhanced interplay between charge excitations and electron-phonon coupling.
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