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

作　　者：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 

机构地区：[1]National Laboratory for Superconductivity, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics,Chinese Academy of Sciences [2]University of Chinese Academy of Sciences [3]Collaborative Innovation Center of Quantum Matter

出　　处：《Chinese Physics B》2017年第7期363-372,共10页中国物理B（英文版）

基　　金：Project supported by the National Natural Science Foundation of China(Grant No.11574360);the National Basic Research Program of China(Grant Nos.2015CB921300,2013CB921700,and 2013CB921904);the National Key Research and Development Program of China(Grant No.2016YFA0300300);the Strategic Priority Research Program(B)of the Chinese Academy of Sciences(Grant No.XDB07020300)

摘　　要：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.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.

关 键 词：iron-based superconductor FeSe film ARPES electronic structure 

分 类 号：O484[理学—固体物理] O511.3[理学—物理]