Pure nematic state in the iron-based superconductor FeSe
Yuya Kubota, F. Nabeshima, K. Nakayama, H. Ohsumi, Yoshikazu Tanaka, Kenji Tamasaku, Takeshi Suzuki, Kozo Okazaki, T. Sato, Atsutaka Maeda, Makina Yabashi
Abstract
Lattice and electronic states of thin FeSe films on ${\mathrm{LaAlO}}_{3}$ substrates are investigated in the vicinity of the nematic phase transition. No evidence of a structural phase transition is found by x-ray diffraction below ${T}^{*}\ensuremath{\sim}90$ K, while results obtained from a resistivity measurement and angle-resolved photoemission spectroscopy clearly show the appearance of a nematic state. These results indicate the formation of a pure nematic state in the iron-based superconductor and provide conclusive evidence that the nematic state originates from the electronic degrees of freedom. This pure nematicity in the thin film implies the difference in the electron-lattice interaction from bulk FeSe crystals. FeSe films provide valuable playgrounds for observing the pure response of ``bare'' electron systems free from the electron-lattice interaction, and should make an important contribution to investigate nematicity and its relationship with superconductivity.