近日，美国加州大学的Xiaoqing Pan及其研究团队取得一项新进展。经过不懈努力，他们对FeSe/SrTiO₃界面处的声子模式和电子-声子耦合进行了研究。相关研究成果已于2024年10月30日在国际权威学术期刊《自然》上发表。

该团队团队利用动量选择高分辨率电子能量损失谱，在原子尺度上解析了FeSe/STO界面处的声子。研究人员在75-99meV的能量范围内发现了新的光学声子模式，这些模式与电子强烈耦合。这些模式的特征是界面双层TiO_x层中氧原子和STO中顶端氧原子的面外振动。

这项研究结果还表明，1uc FeSe/STO的电子-声子耦合（EPC）强度和超导能隙，与FeSe和以TiO_x为终端的STO之间的层间距密切相关。这些发现揭示了界面EPC的微观起源，并为在FeSe/STO以及可能的其他超导系统中，实现大且稳定的T_c增强提供了见解。

据悉，在SrTiO3衬底上的一ucFeSe薄膜（1uc FeSe/STO）界面处，观察到的超导转变温度（T_c）的显著提升，引发了人们对界面效应的广泛研究。尽管人们认为这一高T_c与电子-声子耦合（EPC）有关，但其微观耦合机制及其在超导性中的作用仍不清楚。

附：英文原文

Title: Phonon modes and electron–phonon coupling at the FeSe/SrTiO₃ interface

Author: Yang, Hongbin, Zhou, Yinong, Miao, Guangyao, Rusz, Jn, Yan, Xingxu, Guzman, Francisco, Xu, Xiaofeng, Xu, Xianghan, Aoki, Toshihiro, Zeiger, Paul, Zhu, Xuetao, Wang, Weihua, Guo, Jiandong, Wu, Ruqian, Pan, Xiaoqing

Issue&Volume: 2024-10-30

Abstract: The remarkable increase in superconducting transition temperature (T_c) observed at the interface of one-unit-cell FeSe films on SrTiO₃ substrates (1uc FeSe/STO) has attracted considerable research into the interface effects. Although this high T_c is thought to be associated with electron–phonon coupling (EPC), the microscopic coupling mechanism and its role in the superconductivity remain elusive. Here we use momentum-selective high-resolution electron energy loss spectroscopy to atomically resolve the phonons at the FeSe/STO interface. We uncover new optical phonon modes, coupling strongly with electrons, in the energy range of 75–99meV. These modes are characterized by out-of-plane vibrations of oxygen atoms in the interfacial double-TiO_x layer and the apical oxygens in STO. Our results also demonstrate that the EPC strength and superconducting gap of 1uc FeSe/STO are closely related to the interlayer spacing between FeSe and the TiO_x terminated STO. These findings shed light on the microscopic origin of the interfacial EPC and provide insights into achieving large and consistent T_c enhancement in FeSe/STO and potentially other superconducting systems.

DOI: 10.1038/s41586-024-08118-0

Source: https://www.nature.com/articles/s41586-024-08118-0