Room Temperature Spin-to-Charge Conversion in Amorphous Topological Insulating Gd-Alloyed BixSe1-x/CoFeB Bilayers

Protyush Sahu, Yifei Yang, Yihong Fan, Henri Jaffrès, Jun Yang Chen, Xavier Devaux, Yannick Fagot-Revurat, Sylvie Migot, Enzo Rongione, Tongxin Chen, Pambiang Abel Dainone, Jean Marie George, Sukhdeep Dhillon, Martin Micica, Yuan Lu, Jian Ping Wang

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

Abstract

Disordered topological insulator (TI) films have gained intense interest by benefiting from both the TI’s exotic transport properties and the advantage of mass production by sputtering. Here, we report on the clear evidence of spin-charge conversion (SCC) in amorphous Gd-alloyed BixSe1-x (BSG)/CoFeB bilayers fabricated by sputtering, which could be related to the amorphous TI surface states. Two methods have been employed to study SCC in BSG (tBSG = 6-16 nm)/CoFeB(5 nm) bilayers with different BSG thicknesses. First, spin pumping is used to generate a spin current in CoFeB and detect SCC by the inverse Edelstein effect (IEE). The maximum SCC efficiency (SCE) is measured to be as large as 0.035 nm (IEE length λIEE) in a 6 nm thick BSG sample, which shows a strong decay when tBSG increases due to the increase of BSG surface roughness. The second method is THz time-domain spectroscopy, which reveals a small tBSG dependence of SCE, validating the occurrence of a pure interface state-related SCC. Furthermore, our angle-resolved photoemission spectroscopy data show dispersive two-dimensional surface states that cross the bulk gap until the Fermi level, strengthening the possibility of SCC due to the amorphous TI states. Our studies provide a new experimental direction toward the search for topological systems in amorphous solids.

Original languageEnglish (US)
Pages (from-to)38592-38602
Number of pages11
JournalACS Applied Materials and Interfaces
Volume15
Issue number32
DOIs
StatePublished - Aug 16 2023

Bibliographical note

Publisher Copyright:
© 2023 American Chemical Society.

Keywords

  • THz time-domain spectroscopy
  • amorphous
  • spin pumping
  • spin-to-charge conversion
  • topological insulator

PubMed: MeSH publication types

  • Journal Article

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