Research ArticlePHYSICS

Magnetic and defect probes of the SmB6 surface state

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Science Advances  09 Nov 2018:
Vol. 4, no. 11, eaau4886
DOI: 10.1126/sciadv.aau4886
  • Fig. 1 Tunneling spectra with W and Cr tips.

    Spectra obtained on nonreconstructed surfaces of pure SmB6 by a W tip (red) and a magnetic Cr tip (blue) at 0.35 K and zero magnetic field (Vb = 50 mV; set-point current Isp = 200 pA). For comparison, a spectrum taken with a W tip at a magnetic field of 12 T is presented (pink, vertically offset by 1 nA/V).

  • Fig. 2 Influence of impurities on spectroscopic results.

    (A to C) Topographies (8 nm by 8 nm) of pure SmB6 as well as SmB6:3%Y and SmB6:0.5%Gd. The cyan arrows indicate the ranges and directions of STS measurements around the impurities. (D to F) dI/dV curves of the three samples measured at 0.35 K and zero field. The curves are measured at positions with increasing distance from the impurity (the impurities are located at #1) along the arrows in (A) to (C), correspondingly (Vb = 30 mV; Isp = 100 pA). arb. units, arbitrary units. (G to I) dI/dV values at Vb = −6.5 meV (red) and −2.5 meV (blue) with increasing distance from the impurity (impurities are located at 0). The black dashed lines are fits according to the model (see text S6). hsup and sup indicate the suppression of peak intensity at the impurity and its lateral extent, respectively.

  • Fig. 3 Resistivity of pristine and substituted SmB6.

    (A) Temperature dependence of resistivity ρ of pure and differently substituted SmB6 in double-logarithmic presentation. (B) ln(ρ) versus 1/T plot at intermediate temperatures used to derive the energy gap from thermal excitation. The gap values obtained from the slopes of the pristine (pink dashed line) and the lightly substituted samples (green dashed line) above 20 K (dotted vertical line) are given.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/4/11/eaau4886/DC1

    Text S1. Changing tip conditions on Gd-substituted SmB6

    Text S2. Comparison of spectra with suppressed surface state signature peak

    Text S3. Reconstructed surface of Gd-substituted SmB6

    Text S4. Comparison between SmB6:0.5%Gd and SmB6:3%Gd

    Text S5. Defect analysis of SmB6:3%Y

    Text S6. Analytical solution to the single magnetic impurity

    Fig. S1. STS with a Cr tip in a magnetic field.

    Fig. S2. Converting a nonmagnetic into a magnetic tip.

    Fig. S3. Topographies obtained with a W tip on SmB6:0.5%Gd.

    Fig. S4. Suppression of the surface state signature peak.

    Fig. S5. Disordered reconstructed surface of SmB6:0.5%Gd.

    Fig. S6. Suppression of surface state signature peak on SmB6:3%Gd.

    Fig. S7. Surface of SmB6:3%Y.

  • Supplementary Materials

    This PDF file includes:

    • Text S1. Changing tip conditions on Gd-substituted SmB6
    • Text S2. Comparison of spectra with suppressed surface state signature peak
    • Text S3. Reconstructed surface of Gd-substituted SmB6
    • Text S4. Comparison between SmB6:0.5%Gd and SmB6:3%Gd
    • Text S5. Defect analysis of SmB6:3%Y
    • Text S6. Analytical solution to the single magnetic impurity
    • Fig. S1. STS with a Cr tip in a magnetic field.
    • Fig. S2. Converting a nonmagnetic into a magnetic tip.
    • Fig. S3. Topographies obtained with a W tip on SmB6:0.5%Gd.
    • Fig. S4. Suppression of the surface state signature peak.
    • Fig. S5. Disordered reconstructed surface of SmB6:0.5%Gd.
    • Fig. S6. Suppression of surface state signature peak on SmB6:3%Gd.
    • Fig. S7. Surface of SmB6:3%Y.

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