Interfacial Polarons Driven by Charge Transfer in WSe2/Cuprate Superconductor Systems

Understanding the electronic properties of doped copper-oxygen planes remains a significant challenge in condensed matter physics and is crucial to unraveling the mechanisms behind high-temperature superconductivity in cuprates. Recently, the observation of charge transfer and interfacial polarons in a superconducting interface has aroused extensive research interest. However, experimental data to investigate charge transfer on the CuO₂ plane and the presence of polarons are still missing. Here we conduct extensive research on the optical and electronic properties of 2D materials supported on copper-based superconductors. Unlike monolayer-WSe₂ on other substrates, monolayer-WSe₂ on La_1.85Sr_0.15CuO₄ (WSe₂/LSCO) produces a special band structure. Using high-resolution spectroscopic ellipsometry and density functional theory calculation methods, the special electronic structure can be attributed to the formation of the interfacial small polaron at the WSe₂/LSCO interface which is driven by charge transfer between the CuO₂ plane of the cuprate superconductor and WSe₂. In addition, the structural phase transition of the LSCO substrate was observed to reduce the e-h interaction of WSe₂. These findings may spur future investigations on the effect of the interfacial polaron on the superconductivity of cuprates and highlight the significant influence of interface effects on the electronic structure of WSe₂ films. It provides an effective method to further explore the intrinsic relationship between interfacial polarons and superconductivity.