Quasiparticle coherence in the nematic state of FeSe
Heike Pfau, Ming Yi, Makoto Hashimoto, T. Chen, Pengcheng Dai, Zhi‐Xun Shen, Sung‐Kwan Mo, Dong-Hui Lu
Abstract
Electronic nematicity is a ubiquitous phenomenon in iron-based superconductors but its origin is still debated. Most models consider either spin or orbital degrees of freedom as the driving force but typically do not take electronic correlations into account. However, mass enhancements, coherent-incoherent crossovers, and the strong orbital differentiation can only be understood using correlations in a Hund's metal framework. Here, we study the influence of nematicity on the quasiparticle coherence in detwinned FeSe using angle-resolved photoemission spectroscopy (ARPES). We compare photoemission spectral weight from ${d}_{xz}$ and ${d}_{yz}$ orbitals in the coherent quasiparticle peak and in the incoherent Hubbard band and find an anisotropy between the two orbitals. We interpret our observation in terms of a more coherent ${d}_{xz}$ orbital compared to the ${d}_{yz}$ orbital inside the nematic phase. This result is in contrast to earlier predictions of an incoherent ${d}_{xz}$ orbital and highlights the importance of electronic correlations in the description of nematicity.