Electronic structure and nematic phase transition in superconducting multiple-layer FeSe films grown by pulsed laser deposition method

• Published in: Chinese physics B Vol. 26; no. 7; pp. 363 - 372
• Main Author: 沈兵 冯中沛 黄建伟 胡勇 高强 李聪 徐煜 刘国东 俞理 赵林 金魁 周兴江
• Format: Journal Article
• Language: English
• Published: 01.06.2017
• Subjects: PLD方法; 分子束外延生长; 向列相; 电子结构; 相转变温度; 脉冲激光沉积法; 角分辨光电子能谱; 超导薄膜
• ISSN: 1674-1056; 2058-3834
• DOI: 10.1088/1674-1056/26/7/077402

We report comprehensive angle-resolved photoemission investigations on the electronic structure of single crystal multiple-layer FeSe films grown on CaF_2 substrate by pulsed laser deposition（PLD） method. Measurements on FeSe/CaF_2 samples with different superconducting transition temperatures T_c of 4 K, 9 K, and 14 K reveal electronic difference in their Fermi surface and band structure. Indication of the nematic phase transition is observed from temperature-dependent measurements of these samples; the nematic transition temperature is 140-160 K, much higher than ~90 K for the bulk FeSe. Potassium deposition is applied onto the surface of these samples; the nematic phase is suppressed by potassium deposition which introduces electrons to these FeSe films and causes a pronounced electronic structure change. We compared and discussed the electronic structure and superconductivity of the FeSe/CaF_2 films by PLD method with the FeSe/SrTiO_3 films by molecular beam epitaxy（MBE） method and bulk FeSe. The PLD-grown multilayer FeSe/CaF_2 is more hole-doped than that in MBE-grown multiple-layer FeSe films. Our results on FeSe/CaF_2 films by PLD method establish a link between bulk FeSe single crystal and FeSe/SrTiO_3 films by MBE method, and provide important information to understand superconductivity in FeSe-related systems.