Research ArticlePHYSICS

Particle-hole symmetry reveals failed superconductivity in the metallic phase of two-dimensional superconducting films

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Science Advances  15 Sep 2017:
Vol. 3, no. 9, e1700612
DOI: 10.1126/sciadv.1700612
  • Fig. 1 Electrical transport in disordered superconducting devices.

    (A) Micrograph and schematic diagram of InOx and TaNx Hall bar devices. (B and C) Resistive transitions for the TaNx (B) and InOx (C) films. Left: Zero-field resistivity versus temperature. Right: Resistive transitions in the indicated magnetic field plotted against inverse temperature, highlighting the saturated regime.

  • Fig. 2 Region of zero Hall effect.

    Hall resistivity versus temperature for weakly disordered TaNx (left) and InOx (right) films. The curves are offset vertically according to their temperature; the shaded region indicates where ρxy = 0 as a function of temperature and magnetic field, and an approximate location of Hc2 is marked for each curve. Scale bars for ρxy are shown at the lower right.

  • Fig. 3 Transport regimes in magnetic field.

    Longitudinal resistance (A), transverse resistance (B), scaling of ρxx and ρxy (C), the ratio ρxx2xy (D), and σxy (E) plotted versus magnetic field for three different temperatures for the InOx sample shown in Fig. 2. (A and B) Normal-state (4.2 K) curves, for reference. (C) Regions of linear scaling (lines are guides to the eye). The transition from a true superconductor to an anomalous metallic phase is marked at HM1, the transition from the anomalous metallic phase to a vortex flow–dominated superconductor at HM2, and the mean field transition to the normal state at Hc2. The solid lines in (C) show the dissipative region of vortex motion (see main text); the solid line in (E) shows the normal-state metallic Hall conductivity σxyM.

  • Fig. 4 Schematic phase diagram for a weakly disordered 2D superconductor.

    In zero field, a true superconducting (SC) state with transition temperature TKTB is manifested by zero resistance (see main text). Increasing the magnetic field uncovers a transition to an anomalous metallic (a-Metal) phase at HM1, a transition to a vortex flow–dominated superconductor at HM2, and the mean field transition to the normal state at Hc2 (and Tc0 in zero field). Dashed lines, extracted from observed transitions in the longitudinal and/or transverse resistances, represent finite-temperature crossovers. True phase boundaries lie at H = 0 and in the limit of zero temperature.

Supplementary Materials

  • Supplementary Materials

    This PDF file includes:

    • Additional data—TaNx
    • Hall conductivity in the presence of inhomogeneity
    • fig. S1. Transport regimes in TaNx, comparable to Fig. 3.

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