Temperature-Dependent Anisotropy and Two-Band Superconductivity Revealed by Lower Critical Field in Organic Superconductorκ-(BEDT-TTF)_(2)Cu[N(CN)_(2)]Br  

作　　者：睦惠景 司进 杨琴珪 相英 杨海朋 闻海虎 Huijing Mu;Jin Si;Qingui Yang;Ying Xiang;Haipeng Yang;Hai-Hu Wen(National Laboratory of Solid State Microstructures and Department of Physics,Collaborative Innovation Center of Advanced Microstructures,Nanjing University,Nanjing 210093,China;College of Materials Science and Engineering,Shenzhen Key Laboratory of Polymer Science and Technology,Shenzhen University,Shenzhen 518060,China)

机构地区：[1]National Laboratory of Solid State Microstructures and Department of Physics,Collaborative Innovation Center of Advanced Microstructures,Nanjing University,Nanjing 210093,China [2]College of Materials Science and Engineering,Shenzhen Key Laboratory of Polymer Science and Technology,Shenzhen University,Shenzhen 518060,China

出　　处：《Chinese Physics Letters》2023年第6期56-62,共7页中国物理快报（英文版）

基　　金：the National Natural Science Foundation of China(Grant Nos.11927809 and NSFC-DFG12061131001);National Key Research and Development Program of China(Grant No.2022YFA1403200);the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB25000000)。

摘　　要：Resistivity and magnetization have been measured at different temperatures and magnetic fields in organic superconductorsκ-(BEDT-TTF)_(2)Cu[N(CN)_(2)]Br.The lower critical field and upper critical field are determined,which allow to depict a complete phase diagram.Through the comparison between the upper critical fields with magnetic field perpendicular and parallel to the conducting ac-planes,and the scaling of the in-plane resistivity with field along different directions,we find that the anisotropyΓis strongly dependent on temperature.It is realized thatΓis quite large(above 20)near Tc,which satisfies the 2D model,but approaches a small value in the low-temperature region.The 2D-Tinkham model can also be used to fit the data at high temperatures.This is explained as a crossover from the orbital depairing mechanism in high-temperature and low-field region to the paramagnetic depairing mechanism in the high-field and low-temperature region.The temperature dependence of lower critical field,Hc1(T),shows a concave shape in wide temperature region.It is found that neither a single d-wave nor a single s-wave gap can fit the Hc1(T),however a two-gap model containing an s-wave and a d-wave can fit the data rather well,suggesting two-band superconductivity and an unconventional pairing mechanism in this organic superconductor.

关 键 词：temperature satis DIRECTIONS 

分 类 号：O511[理学—低温物理]