High-resolution RIXS study of the relation between acoustic plasmons and superconductivity in cuprates

Despite more than 30 years of intense research on high-Tc superconducting cuprates, a comprehensive understanding of the mechanisms that lead to their exceptionally strong superconductivity has remained elusive. Using Cu L3-edge resonant inelastic x-ray scattering (RIXS), three-dimensional collective charge excitations were revealed in electron-doped cuprates, which subsequently were also observed in hole-doped cuprates by O K-edge RIXS. Interestingly, these collective excitations correspond to the long-anticipated acoustic plasmon modes of cuprates, which were suggested to contribute to the mediation of superconducting pairing, and their evolution across Tc could reflect a possible saving of kinetic energy correlated with the superconducting transition. Here we propose an O K-edge RIXS study on the hole-doped cuprate YBa2Cu3O7 to investigate the behavior of acoustic plasmons above and below the superconducting transition and a possible relation to the elevated Tc of cuprates.

尽管针对高温铜基超导体（high-Tc superconducting cuprates）已开展三十余年的深入研究，但学界始终未能对其超强超导性的形成机制达成全面清晰的认知。研究人员通过铜L3边共振非弹性X射线散射（Cu L3-edge resonant inelastic x-ray scattering, RIXS），在电子掺杂铜基超导体中观测到三维集体电荷激发模式；后续借助氧K边共振非弹性X射线散射（O K-edge RIXS），也在空穴掺杂铜基超导体中发现了此类集体激发。值得注意的是，这类集体激发对应着学界长期期盼的铜基超导体声学等离激元模式，该模式被认为可介导超导配对；且其在超导临界转变温度（Tc）上下的演化特征，或可反映与超导转变相关的动能节约现象。本研究提出，将通过氧K边共振非弹性X射线散射对空穴掺杂铜基超导体YBa2Cu3O7开展研究，以探究声学等离激元在超导临界转变温度上下的行为，及其与铜基超导体升高的Tc之间的潜在关联。