摘要
In the phase diagram of the nickel-based superconductor Ba_(1-x)Sr_(x)Ni_(2)As_(2),T_(C) has been found to be enhanced sixfold near the quantum critical point(QCP) x=0.71 compared with the parent compound.However,the mechanism is still under debate.Here,we report a detailed investigation of the superconducting properties near the QCP(x≈0.7) by utilizing scanning tunneling microscopy and spectroscopy.The temperature-dependent superconducting gap and magnetic vortex state were obtained and analyzed in the framework of the Bardeen-Cooper-Schrieffer model.The ideal isotropic s-wave superconducting gap excludes the long-speculated nematic fluctuations while preferring strong electron-phonon coupling as the mechanism for T_(C) enhancement near the QCP.The lower than expected gap ratio of Δ/(k_(B) T_(C)) is rooted in the fact that Ba_(1-x)Sr_(x)Ni_(2)As_(2) falls into the dirty limit with a serious pair breaking effect similar to the parent compound.
作者
余承峰
张宗源
宋林兴
吴彦玮
袁小秋
侯杰
涂玉兵
侯兴元
李世亮
单磊
Chengfeng Yu;Zongyuan Zhang;Linxing Song;Yanwei Wu;Xiaoqiu Yuan;Jie Hou;Yubing Tu;Xingyuan Hou;Shiliang Li;Lei Shan(Information Materials and Intelligent Sensing Laboratory of Anhui Province,Institutes of Physical Science and Information Technology,Anhui University,Hefei 230601,China;Key Laboratory of Structure and Functional Regulation of Hybrid Materials(Anhui University),Ministry of Education,Hefei 230601,China;Beijing National Laboratory for Condensed Matter Physics,Institute of Physics,Chinese Academy of Sciences,Beijing 100190,China;School of Physical Sciences,University of Chinese Academy of Sciences,Beijing 100190,China;Songshan Lake Materials Laboratory,Dongguan 523808,China)
基金
Project supported by the National Key R&D Program of China (Grant Nos. 2022YFA1403203, 2022YFA1403400, and 2021YFA1400400)
the Innovation Program for Quantum Science and Technology (Grant No. 2021ZD0302802)
the National Natural Science Foundation of China (Grant Nos. 12074002, 12104004, 12204008, and 12374133)
the Chinese Academy of Sciences (Grant Nos. XDB33000000 and GJTD-2020-01)
the Major Basic Program of Natural Science Foundation of Shandong Province (Grant No. ZR2021ZD01)。
