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Title: Thin films of topological Kondo insulator candidate SmB 6: Strong spin-orbit torque without exclusive surface conduction

Abstract

The advent of topological insulators (TIs), a novel class of materials that harbor a metallic spin-chiral surface state coexisting with band-insulating bulk, opens up new possibilities for spintronics. One promising route is current-induced switching of an adjacent magnetic layer via spin-orbit torque (SOT), arising from the large spin-orbit coupling intrinsically possessed by TIs. The Kondo insulator SmB 6 has been recently proposed to be a strongly correlated TI, supported by the observation of a metallic surface state in bulk SmB 6, as evidenced by the thickness independence of the low-temperature resistance plateau. We report the synthesis of epitaxial (001) SmB 6/Si thin films and a systematic thickness-dependent electrical transport study. Although the low-temperature resistance plateau is observed for all films from 50 to 500 nm in thickness, the resistance is distinctively thickness-dependent and does not support the notion of surface conduction and interior insulation. On the other hand, we demonstrate that SmB 6 can generate a large SOT to switch an adjacent ferromagnetic layer, even at room temperature. The effective SOT generated from SmB 6 is comparable to that from β-W, one of the strongest SOT materials.

Authors:
ORCiD logo [1];  [1]; ORCiD logo [1]; ORCiD logo [1]
  1. Johns Hopkins Univ., Baltimore, MD (United States)
Publication Date:
Research Org.:
Johns Hopkins Univ., Baltimore, MD (United States); Univ. of California, Riverside, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1499931
Grant/Contract Number:  
SC0009390; SC0012670
Resource Type:
Accepted Manuscript
Journal Name:
Science Advances
Additional Journal Information:
Journal Volume: 4; Journal Issue: 1; Journal ID: ISSN 2375-2548
Publisher:
AAAS
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; 36 MATERIALS SCIENCE

Citation Formats

Li, Yufan, Ma, Qinli, Huang, S. X., and Chien, C. L. Thin films of topological Kondo insulator candidate SmB6: Strong spin-orbit torque without exclusive surface conduction. United States: N. p., 2018. Web. doi:10.1126/sciadv.aap8294.
Li, Yufan, Ma, Qinli, Huang, S. X., & Chien, C. L. Thin films of topological Kondo insulator candidate SmB6: Strong spin-orbit torque without exclusive surface conduction. United States. doi:10.1126/sciadv.aap8294.
Li, Yufan, Ma, Qinli, Huang, S. X., and Chien, C. L. Fri . "Thin films of topological Kondo insulator candidate SmB6: Strong spin-orbit torque without exclusive surface conduction". United States. doi:10.1126/sciadv.aap8294. https://www.osti.gov/servlets/purl/1499931.
@article{osti_1499931,
title = {Thin films of topological Kondo insulator candidate SmB6: Strong spin-orbit torque without exclusive surface conduction},
author = {Li, Yufan and Ma, Qinli and Huang, S. X. and Chien, C. L.},
abstractNote = {The advent of topological insulators (TIs), a novel class of materials that harbor a metallic spin-chiral surface state coexisting with band-insulating bulk, opens up new possibilities for spintronics. One promising route is current-induced switching of an adjacent magnetic layer via spin-orbit torque (SOT), arising from the large spin-orbit coupling intrinsically possessed by TIs. The Kondo insulator SmB6 has been recently proposed to be a strongly correlated TI, supported by the observation of a metallic surface state in bulk SmB6, as evidenced by the thickness independence of the low-temperature resistance plateau. We report the synthesis of epitaxial (001) SmB6/Si thin films and a systematic thickness-dependent electrical transport study. Although the low-temperature resistance plateau is observed for all films from 50 to 500 nm in thickness, the resistance is distinctively thickness-dependent and does not support the notion of surface conduction and interior insulation. On the other hand, we demonstrate that SmB6 can generate a large SOT to switch an adjacent ferromagnetic layer, even at room temperature. The effective SOT generated from SmB6 is comparable to that from β-W, one of the strongest SOT materials.},
doi = {10.1126/sciadv.aap8294},
journal = {Science Advances},
number = 1,
volume = 4,
place = {United States},
year = {2018},
month = {1}
}

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Figures / Tables:

Fig. 1. Fig. 1.: Crystal structure characterization and transport properties of SmB6 thin films. (A) Crystal structure of SmB6 (top) and epitaxy relation of SmB6/Si(001). (B) Out-of-plane θ/2θ XRD of the 250-nm-thick SmB6/Si(001) film. (C) In-plane f scan of the Si(220) peak (top) and the SmB6(110) peak (bottom). (D) Temperature dependence ofmore » the sheet resistance for the 250-nm-thick film of SmB6/Si(001). Inset: Representative Arrhenius plot of Gmeasured − Gplateau as a function of 1/T for the 250-nm-thick film, from 50 to 5 K. The red curve shows the linear fitting of ln Ginsulator versus 1/T. (E) Activation energy Δ derived from the Arrhenius plot for various film thicknesses. The dashed lines denote Δ values reported in previous bulk SmB6 studies (18, 19, 35).« less

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    Figures/Tables have been extracted from DOE-funded journal article accepted manuscripts.