The discovery of high-temperature (high-T_c) superconductivity in one-monolayer FeSe on SrTiO₃ has attracted tremendous attention. Subsequent studies suggested the importance of cooperation between intra-FeSe-layer and interfacial interactions to enhance T_c. However, the nature of intra-FeSe-layer interactions, which would play a primary role in determining the pairing symmetry, remains unclear. Here we have performed high-resolution angle-resolved photoemission spectroscopy of one-monolayer and alkaline-metal-deposited multilayer FeSe films on SrTiO₃, and determined the evolution of quasiparticle band dispersion across T_c. We found that the band dispersion in the superconducting state deviates from the Bogoliubov-quasiparticle dispersion expected from the normal-state band dispersion with a constant gap size. This suggests highly anisotropic pairing originating from small momentum transfer and/or mass renormalization due to electron–boson coupling. This band anomaly is interpreted in terms of the electronic interactions within the FeSe layers that may be related to the high-T_c superconductivity in electron-doped FeSe.

中文翻译：

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电子掺杂FeSe薄膜中准粒子能带色散的异常温度演化

在SrTiO ₃上单层FeSe中的高温（高T _c）超导性的发现引起了极大的关注。随后的研究表明FeSe层内和界面相互作用之间合作以提高T _c的重要性。然而，FeSe层内相互作用的性质（在确定配对对称性中起主要作用）尚不清楚。在这里，我们对SrTiO ₃上的单层和碱金属沉积的多层FeSe膜进行了高分辨率的角分辨光发射光谱学，并确定了在T _c上准粒子带分散的演变。我们发现，超导状态下的能带色散不同于具有恒定间隙尺寸的正常态能带色散所期望的Bogoliubov-准粒子色散。这表明高度各向异性的配对源于小动量传递和/或由于电子-玻色子耦合而引起的质量重正化。该带异常被解释在FESE层内的电子的相互作用可能涉及到高的术语Ť _Ç超导在电子掺杂FESE。