Resolving Phonons in Superconductor Bi2Sr2CaCu2O8+{\delta} at Sub-Unit-Cell Resolution

Xiaowen Zhang; Jiade Li; Xiaoyue Gao; Ruochen Shi; Bo Han; Xiaomei Li; Jinlong Du; Jinsheng Wen; Genda Gu; Shichong Wang; Wentao Zhang; Peng Gao

arXiv · 2506.14127

Resolving Phonons in Superconductor Bi2Sr2CaCu2O8+{\delta} at Sub-Unit-Cell Resolution

Xiaowen Zhang·Jiade Li·Xiaoyue Gao·Ruochen Shi·Bo Han·Xiaomei Li·Jinlong Du·Jinsheng Wen·Genda Gu·Shichong Wang·Wentao Zhang·Peng Gao

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Abstract

The role of phonons in cuprates remains controversial, with their complex lattice structure complicating the investigation. Here, we identify phonon modes originating from charge reservoir and superconducting layers of Bi2Sr2CaCu2O8+{\delta} using sub-unit-cell resolved electron energy loss spectroscopy in a scanning transmission electron microscope. We reveal several phonon modes exhibiting layer-specific localization: ~78 meV in-plane modes localized in the CuO2 planes, ~42 meV hybrid (in-plane and out-of-plane) modes in the CuO2 planes, and ~38 meV hybrid modes in the BiO layers. We also observe a periodic modulation of phonon frequencies induced by the superstructure, spatially correlating with the superconducting gap variation. Our findings offer new insights into the electron-phonon coupling in cuprates, fostering deeper exploration of the microscopic linkage between lattice dynamics and superconductivity.

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Xiaowen Zhang, Jiade Li, Xiaoyue Gao, Ruochen Shi, Bo Han, Xiaomei Li, Jinlong Du, Jinsheng Wen, Genda Gu, Shichong Wang, Wentao Zhang, Peng Gao. 2025-06-17. Resolving Phonons in Superconductor Bi2Sr2CaCu2O8+{\delta} at Sub-Unit-Cell Resolution. https://arxiv.org/abs/2506.14127

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