A new Majorana platform in an Fe-As bilayer superconductor
Wenyao Liu, Lu Cao, Shiyu Zhu, Lingyuan Kong, Guangwei Wang, Michał Papaj, Peng Zhang, Ya-Bin Liu, Hui Chen, Geng Li, Fazhi Yang, Takeshi Kondo, Shixuan Du, Guang-Han Cao, Shik Shin, Liang Fu, Zhiping Yin, Hong-Jun Gao, Hong Ding
Abstract
Abstract Iron-chalcogenide superconductors have emerged as a promising Majorana platform for topological quantum computation. By combining topological band and superconductivity in a single material, they provide significant advantage to realize isolated Majorana zero modes. However, iron-chalcogenide superconductors, especially Fe(Te,Se), suffer from strong inhomogeneity which may hamper their practical application. In addition, some iron-pnictide superconductors have been demonstrated to have topological surface states, yet no Majorana zero mode has been observed inside their vortices, raising a question of universality about this new Majorana platform. In this work, through angle-resolved photoemission spectroscopy and scanning tunneling microscopy/spectroscopy measurement, we identify Dirac surface states and Majorana zero modes, respectively, for the first time in an iron-pnictide superconductor, CaKFe 4 As 4 . More strikingly, the multiple vortex bound states with integer-quantization sequences can be accurately reproduced by our model calculation, firmly establishing Majorana nature of the zero mode.