Observation of Majorana fermions in ferromagnetic atomic chains on a superconductor
Majorana fermions are predicted to localize at the edge of a topological superconductor, a state of matter that can form when a ferromagnetic system is placed in proximity to a conventional superconductor with strong spin-orbit interaction. With the goal of realizing a one-dimensional topological superconductor, we have fabricated ferromagnetic iron (Fe) atomic chains on the surface of superconducting lead (Pb). Using high-resolution spectroscopic imaging techniques, we show that the onset of superconductivity, which gaps the electronic density of states in the bulk of the Fe chains, is accompanied by the appearance of zero-energy end-states. This spatially resolved signature provides strong evidence, corroborated by other observations, for the formation of a topological phase and edge-bound Majorana fermions in our atomic chains.
Additional Information© 2014 American Association for the Advancement of Science. 28 July 2014; accepted 19 September 2014. Published online 2 October 2014. We thank F. von Oppen, L. Glazman, D. Loss, A. Stern, J. Alicea, M. Franz, R. Lutchyn, C.-K. Shih, B. Feldman, M. Randeria, P. Lee, and N. P. Ong for helpful discussions. The work at Princeton University has been primarily supported by Majorana Basic Research Challenge grant through ONR-N00014-14-1-0330, ONR-N00014-11-1-0635, ONR- N00014-13-10661, NSF–Materials Research Science and Engineering Center programs through the Princeton Center for Complex Materials DMR-0819860, and NSF CAREER DMR-095242. Work at the University of Texas at Austin was supported by ONR-N00014-14-1-0330 and the Welch Foundation grant TBF1473. This project was also made possible using the facilities at Princeton Nanoscale Microscopy Laboratory supported by grants through NSF-DMR-1104612, ARO-W911NF-1-0262, ARO-MURI program W911NF-12-1-0461, U.S. Department of Energy Office of Basic Energy Sciences, DARPA-SPWAR Meso program N6601-11-1-4110, Laboratory for Physical Sciences and ARO-W911NF-1-0606, and the W. Keck Foundation. A.Y., B.A.B., and Princeton University have filed a provisional patent related to this work. S.N.-P. acknowledges support of the European Union Marie Curie program (IOF 302937); J.L. acknowledges support of the Swiss National Science Foundation; and A.Y. acknowledges the hospitality of the Aspen Center for Physics, supported under NSF grant PHYS-1066293.
Submitted - 1410.0682v1.pdf