Author:
Zhan 詹 Hong-Xing 红星,Lin 林 Yu-Chi 玉尺,Zhao 赵 Yu-Qing 宇清,Zuo 左 Hai-Yan 海艳,Wang 王 Xing-Yu 兴玉,Ma 马 Xiao-Yan 肖燕,Li 李 Chun-Hong 春红,Luo 罗 Hui-Qian 会仟,Chen 陈 Gen-Fu 根富,Li 李 Shi-Liang 世亮,Ren 任 Cong 聪
Abstract
We report on soft c-axis point-contact Andreev reflection (PCAR) spectroscopy combining with resistivity measurements on BaFe2(As0.7P0.3)2, to elucidate the superconducting gap structure in the vicinity of the quantum critical point. A double peak at the gap edge plus a dip feature at zero-bias has been observed on the PCAR spectra, indicative of the presence of a nodeless gap in BaFe2(As0.7P0.3)2. Detailed analysis within a sophisticated theoretical model reveals an anisotropic gap with deep gap minima. The PCARs also feature additional structures related to the electron–bosonic coupling mode. Using the extracted superconducting energy gap value, a characteristic bosonic energy Ω
b and its temperature dependence are obtained, comparable with the spin-resonance energy observed in neutron scattering experiment. These results indicate a magnetism-driven quantum critical point in the BaFe2(As1−x
P
x
)2 system.