High-resolution studies of the Majorana atomic chain platform

• Published in: Nature physics Vol. 13; no. 3; pp. 286 - 291
• Main Authors: Feldman, Benjamin E., Randeria, Mallika T., Li, Jian, Jeon, Sangjun, Xie, Yonglong, Wang, Zhijun, Drozdov, Ilya K., Andrei Bernevig, B., Yazdani, Ali
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.03.2017; Nature Publishing Group; Nature Publishing Group (NPG)
• Subjects: 639/766/119/1003; 639/766/119/995; Atomic; Atoms & subatomic particles; Chains; Classical and Continuum Physics; Complex Systems; Condensed matter; Condensed Matter Physics; Electric properties; Hybridization; Mathematical and Computational Physics; Microscopy; Molecular; Optical and Plasma Physics; Physics; Refrigerators; Searching; Signatures; Superconductivity; Superconductors; Theoretical; Topology
• ISSN: 1745-2473; 1745-2481
• DOI: 10.1038/nphys3947

Ordered assemblies of magnetic atoms on the surface of conventional superconductors can be used to engineer topological superconducting phases and realize Majorana fermion quasiparticles (MQPs) in a condensed matter setting. Recent experiments have shown that chains of Fe atoms on Pb generically have the required electronic characteristics to form a one-dimensional topological superconductor and have revealed spatially resolved signatures of localized MQPs at the ends of such chains. Here we report higher-resolution measurements of the same atomic chain system performed using a dilution refrigerator scanning tunnelling microscope (STM). With significantly better energy resolution than previous studies, we show that the zero-bias peak (ZBP) in Fe chains has no detectable splitting from hybridization with other states. The measurements also reveal that the ZBP exhibits a distinctive ‘double eye’ spatial pattern on nanometre length scales. Theoretically we show that this is a general consequence of STM measurements of MQPs with substantial spectral weight in the superconducting substrate, a conclusion further supported by measurements of Pb overlayers deposited on top of the Fe chains. Finally, we report experiments performed with superconducting tips in search of the particle–hole symmetric MQP signature expected in such measurements. High-resolution scanning tunnelling microscopy measurements show that chains of magnetic atoms on the surface of a superconductor provide a promising platform for realizing and manipulating Majorana fermion quasiparticles.