Sensitivity of the superconducting state in thin films

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Science Advances  15 Mar 2019:
Vol. 5, no. 3, eaau3826
DOI: 10.1126/sciadv.aau3826
  • Fig. 1 Eliminating saturation.

    (A and C) System structure and (B and D) microscope image of a:InO (AD12a) and 2H-NbSe2 (024) films, respectively. (E and F) R versus T−1 obtained from an a:InO film at B = 7 and 8 T, and a quad-layer 2H-NbSe2 at B = 2.3 and 3.5 T, respectively. Blue traces are measured with, and red traces without, filters. The top axis indicates the corresponding T’s. The black dashed lines in (E) are guides to the eye, indicating activated behavior. The data were measured by applying a standard four-terminal lock-in technique with I0 = 1 (a:InO) and 100 (2H-NbSe2) nA.

  • Fig. 2 Fully recovered activated behavior.

    R versus T−1 obtained from IT1b20, an a:InO film, measured with better filtration (see Materials and Methods for details) at different B values. Activated behavior (straight line in an Arrhenius plot) is apparent down to our noise floor or lowest measurement T’s (see, e.g., dashed black lines at B = 10.75 and 12.3 T).

  • Fig. 3 Resistive transition.

    (A) Measurements of the T-driven (left) and B-driven (right) superconducting-normal phase transition in a 2H-NbSe2 film (024). Blue traces are measured with, and red traces without, filters. (B) BT phase diagram. The black line separating the superconducting and normal phases, defined by R = 0.9∙RN, is obtained from the 2H-NbSe2 sample and includes data that were left out from (A) for visibility. The T and B values, where ΔR/RF = (RUnfilteredRFiltered)/RFiltered = 3%, are marked in both (A) and (B) by green triangles. Both TC and HC2 are defined at R = 0.9∙RN. For our a:InO films, blue and red triangles, we used TC = 2.5 K (Ad12a) and 3 K (IT1b5).

  • Fig. 4 Induced saturation and saturation T.

    (A) V/I versus T−1 obtained from an a:InO film, measured at B = 10 T with increasing I0’s. (B) dV/dI versus T−1 obtained from a 2H-NbSe2 film, measured at B = 2.3 T with an increasing level of IDC (see Materials and Methods). In both (A) and (B), we include one trace (red) measured, at our lowest I, without filters. (C) TsatI versus p extracted from the a:InO data presented in (A) (circles), and the 2H-NbSe2 data presented in (B) (triangles), adopting the same color scale for the different I’s. The red symbols represent Tsatr extracted from the unfiltered measurements. The a:InO data include IAC’s left out of (A) for visibility. These curves are used as p meters to estimate pr = 1.8 and 8.2 × 104 W/cm3 for the a:InO and 2H-NbSe2 samples, respectively. (D) Tsat versus B evaluated for several samples. Our data are plotted in blue (a:InO) and green (2H-NbSe2). The MoGe (10), Ta (11), and ZrNCl (15) data (black symbols) were extracted from the cited references. Full symbols represent data that were calculated using filtered measurements as a thermometer, while data plotted with empty symbols were estimated following the procedure in (10). All samples exhibit similar logarithmic B dependence (see dashed black lines).

Supplementary Materials

  • Supplementary Materials

    This PDF file includes:

    • Fig. S1. Schematics of the measurement circuit.
    • Fig. S2. Probe transmission.
    • Fig. S3. Activation energy.
    • Table S1. Sample parameters.
    • References (3840)

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