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Majorana spin in magnetic atomic chain systems

Author(s): Li, Jian; Jeon, Sangjun; Xie, Yonglong; Yazdani, Ali; Bernevig, Bogdan A.

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Abstract: In this paper, we establish that Majorana zero modes emerging from a topological band structure of a chain of magnetic atoms embedded in a superconductor can be distinguished from trivial localized zero energy states that may accidentally form in this system using spin-resolved measurements. To demonstrate this key Majorana diagnostics, we study the spin composition of magnetic impurity induced in-gap Shiba states in a superconductor using a hybrid model. By examining the spin and spectral densities in the context of the Bogoliubov-de Gennes (BdG) particle-hole symmetry, we derive a sum rule that relates the spin densities of localized Shiba states with those in the normal state without superconductivity. Extending our investigations to a ferromagnetic chain of magnetic impurities, we identify key features of the spin properties of the extended Shiba state bands, as well as those associated with a localized Majorana end mode when the effect of spin-orbit interaction is included. We then formulate a phenomenological theory for the measurement of the local spin densities with spin-polarized scanning tunneling microscopy (STM) techniques. By combining the calculated spin densities and the measurement theory, we show that spin-polarized STM measurements can reveal a sharp contrast in spin polarization between an accidental-zero-energy trivial Shiba state and a Majorana zero mode in a topological superconducting phase in atomic chains. We further confirm our results with numerical simulations that address generic parameter settings.
Publication Date: 15-Mar-2018
Electronic Publication Date: 15-Mar-2018
Citation: Li, Jian, Jeon, Sangjun, Xie, Yonglong, Yazdani, Ali, Bernevig, B Andrei. (2018). Majorana spin in magnetic atomic chain systems. PHYSICAL REVIEW B, 97 (10.1103/PhysRevB.97.125119
DOI: doi:10.1103/PhysRevB.97.125119
ISSN: 2469-9950
EISSN: 2469-9969
Language: English
Type of Material: Journal Article
Journal/Proceeding Title: PHYSICAL REVIEW B
Version: Author's manuscript

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