Chiral Majorana Modes

An emerging approach to quantum computing seeks to utilize topologically protected quantum states as Qubits to solve the error-correction problem, as the information encoded in such a "topological quantum computer" cannot be easily corrupted. A recent focus in condensed matter physics has been finding and fabricating such topological materials. In this talk, I will discuss two material systems that could host chiral Majorana modes and may have potential applications in topological quantum computing. The first system is the interface between a magnetically doped topological insulator and a superconductor, where we found experimental transport evidence for a chiral edge state of Majorana Fermions, which were proposed theoretically by Ettore Majorana in the 1930s by remained elusive. The second system is the ultra-thin bilayer film of bismuth and nickel, where we found experimental optical evidence for a superconducting state that breaks time-reversal symmetry, pointing to a 'd+id' superconducting state. Theories suggest that this state may have two chiral Majorana edge modes propagating around the sample edge, either clockwise or counterclockwise. These Majorana edge states, with further engineering and manipulation, could be useful for topological quantum computing. The works presented here were performed in collaboration with Qing Lin He, Lei Pan, Alexander L. Stern, Edward Burks, Xiaoyu Che, Gen Yin, Jing Wang, Biao Lian, Quan Zhou, Eun Sang Choi, Koichi Murata, Xufeng Kou, Tianxiao Nie, Qiming Shao, Yabin Fan, Shou-Cheng Zhang, Kai Liu, Kang L. Wang (Science, 357(6348), 294–299 (2017)) , and in collaboration with Xinxin Gong, Mehdi Kargarian, Alex Stern, Di Yue, Hexin Zhou, Xiaofeng Jin, Victor M. Galitski, Victor M. Yakovenko. (Science Advances, 3, 3, e1602579 (2017))