Guan Jian-Yu, Kong Lingyuan, Zhou Li-Qin, Zhong Yi-Gui, Li Hang, Liu Hai-Jiang, Tang Cen-Yao, Yan Da-Yu, Yang Fa-Zhi, Huang Yao-Bo, Shi You-Guo, Qian Tian, Weng Hong-Ming, Sun Yu-Jie, Ding Hong
Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China; School of Physics, University of Chinese Academy of Sciences, Beijing 100190, China.
Shanghai Synchrotron Radiation Facility, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201204, China.
Sci Bull (Beijing). 2019 Sep 15;64(17):1215-1221. doi: 10.1016/j.scib.2019.07.019. Epub 2019 Jul 19.
Connate topological superconductor (TSC) combines topological surface states with nodeless superconductivity in a single material, achieving effective p-wave pairing without interface complication. By combining angle-resolved photoemission spectroscopy and in-situ molecular beam epitaxy, we studied the momentum-resolved superconductivity in β-BiPd film. We found that the superconducting gap of topological surface state (Δ ∼ 3.8 meV) is anomalously enhanced from its bulk value (Δ ∼ 0.8 meV). The ratio of 2Δ/kT ∼ 16.3, is substantially larger than the BCS value. By measuring β-BiPd bulk single crystal as a comparison, we clearly observed the upward-shift of chemical potential in the film. In addition, a concomitant increasing of surface weight on the topological surface state was revealed by our first principle calculation, suggesting that the Dirac-fermion-mediated parity mixing may cause this anomalous superconducting enhancement. Our results establish β-BiPd film as a unique case of connate TSCs with a highly enhanced topological superconducting gap, which may stabilize Majorana zero modes at a higher temperature.
本征拓扑超导体（TSC）在单一材料中将拓扑表面态与无节点超导性相结合，实现了有效的p波配对且无界面复杂性。通过结合角分辨光电子能谱和原位分子束外延技术，我们研究了β-BiPd薄膜中的动量分辨超导性。我们发现拓扑表面态的超导能隙（Δ ∼ 3.8 meV）相对于其体值（Δ ∼ 0.8 meV）异常增强。2Δ/kT ∼ 16.3的比值显著大于BCS值。通过测量β-BiPd体单晶作为对比，我们清楚地观察到薄膜中化学势的上移。此外，我们的第一性原理计算揭示了拓扑表面态上表面权重的伴随增加，表明狄拉克费米子介导的宇称混合可能导致这种异常的超导增强。我们的结果确立了β-BiPd薄膜作为具有高度增强拓扑超导能隙的本征TSC的独特案例，这可能在更高温度下稳定马约拉纳零模。
