Temperature and doping dependent flat-band superconductivity on the Lieb-lattice  

作　　者：Feng Xu Lei Zhang Li-Yun Jiang 徐峰;张磊;姜立运(School of Physics and Telecommunication Engineering,Shaanxi University of Technology,Hanzhong 723001,China;Institute of Graphene at Shaanxi Key Laboratory of Catalysis,Shaanxi University of technology,Hanzhong 723001,China)

机构地区：[1]School of Physics and Telecommunication Engineering,Shaanxi University of Technology,Hanzhong 723001,China [2]Institute of Graphene at Shaanxi Key Laboratory of Catalysis,Shaanxi University of technology,Hanzhong 723001,China

出　　处：《Chinese Physics B》2021年第6期541-546,共6页中国物理B（英文版）

基　　金：supported by the National Natural Science Foundation of China (Grant No. 11804213);the Scientific Research Program Funded by Shaanxi Provincial Education Department (Grant No. 20JK0573);the Scientific Research Foundation of Shaanxi University of Technology (Grant No. SLGRCQD2006);the Natural Science Basic Research Program of Shaanxi (Grant No. 2021JQ-748)。

摘　　要：We consider the superconducting properties of Lieb lattice, which produces a flat-band energy spectrum in the normal state under the strong electron–electron correlation. Firstly, we show the hole-doping dependent superconducting order amplitude with various electron–electron interaction strengths in the zero-temperature limit. Secondly, we obtain the superfluid weight and Berezinskii–Kosterlitz–Thouless(BKT) transition temperature with a lightly doping level. The large ratio between the gap-opening temperature and BKT transition temperature shows similar behavior to the pseudogap state in high-T_(c) superconductors. The BKT transition temperature versus doping level exhibits a dome-like shape in resemblance to the superconducting dome observed in the high-T_(c) superconductors. However, unlike the exponential dependence of T_(c) on the electron–electron interaction strength in the conventional high-T_(c) superconductors, the BKT transition temperature for a flat band system depends linearly on the electron–electron interaction strength. We also show the doping-dependent superconductivity on a lattice with the staggered hoping parameter in the end. Our predictions are amenable to verification in the ultracold atoms experiment and promote the understanding of the anomalous behavior of the superfluid weight in the high-T_(c) superconductors.

关 键 词：flat-band superconductivity strong electron–electron interaction superfluid weight Berezinskii–Kosterlitz–Thouless(BKT)transition temperature 

分 类 号：O469[理学—凝聚态物理]