Abstract
In the phase diagram of the nickel-based superconductor Ba1-xSrvNi2As2,Tc 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 Tc enhancement near the QCP.The lower than expected gap ratio of Δ/(kBTc)is rooted in the fact that Ba1-xSrxNi2As2 falls into the dirty limit with a serious pair breaking effect similar to the parent compound.
基金项目
国家重点研发计划(2022YFA1403203)
国家重点研发计划(2022YFA1403400)
国家重点研发计划(2021YFA1400400)
Innovation Program for Quantum Science and Technology(2021ZD0302802)
国家自然科学基金(12074002)
国家自然科学基金(12104004)
国家自然科学基金(12204008)
国家自然科学基金(12374133)
中国科学院项目(XDB33000000)
中国科学院项目(GJTD-2020-01)
Major Basic Program of Natural Science Foundation of Shandong Province(ZR2021ZD01)
NETL
NSTL
万方数据