Research ArticlePHYSICS

Kinetic approach to superconductivity hidden behind a competing order

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Science Advances  05 Oct 2018:
Vol. 4, no. 10, eaau3489
DOI: 10.1126/sciadv.aau3489
  • Fig. 1 Scheme for thermodynamic and kinetic approaches to realizing superconductivity in certain strongly correlated electron systems.

    The conceptual electronic phase diagram considered in this study is displayed with pressure/carrier doping as a control parameter. The double well and ball represent temperature-dependent schematic free-energy landscapes and realized electronic states in each cooling process, respectively. The thermodynamic approach, which can be advanced by increasing pressure or carrier doping, results in a change in the lowest free-energy state, from a certain competing order to a superconducting (SC) state. By contrast, the kinetic approach, which can be advanced by rapid cooling, allows the system to kinetically avoid the first-order phase transition to the competing order and thus to remain in a metastable supercooled state, which is expected to eventually turn into superconducting at low temperatures.

  • Fig. 2 Demonstration of the kinetic approach to a superconducting state in nondoped IrTe2.

    (A) Electronic phase diagram of Pd-doped IrTe2. CO and SC denote the charge-ordered and superconducting phases, respectively. The open diamonds represent the onset temperature of the emergent superconductivity in the quenched metastable state of nondoped IrTe2 samples: #2 and #3. The data for the doped materials are taken from (13). (B) Photograph of a submicrometer-thick IrTe2. (C) Schematic of the current pulse–based rapid-cooling method used in this study. At the end of an electric pulse, a large thermal gradient is realized between the sample and the substrate, thus enabling the rapid cooling of the sample after the pulse ends. The schematic is a result of our numerical simulation (see Materials and Methods and the Supplementary Materials). (D and F) Overall temperature-resistivity profiles of samples #1 (D) and #2 (F), the volumes of which are ≈130 and 15 μm3, respectively. (E and G) Temperature-resistivity profiles of samples #1 (E) and #2 (G) near the superconductivity-onset temperature, which is measured after being slowly cooled and thermally quenched to 4 K.

  • Fig. 3 Contour plot of the electric resistivity postquenching to 4 K at various quenching rates in sample #3.

    This figure represents an interplay between the quenching rate and the emergent superconductivity in nondoped IrTe2. To clearly show the superconducting-transition onset, the data are normalized by the value at 4 K postquenching at each quenching rate.

  • Fig. 4 Nonvolatile superconducting phase change by the application of current pulses.

    (A) Scheme for repeatable switching between the superconducting and charge-ordered states in terms of a schematic free-energy landscape and the kinetic approach. In the SET process, the application of a high-intensity current pulse results in the rapid cooling of the sample from a temperature above the charge ordering. In the RESET process, a pulse with moderate intensity and longer width is applied to heat the quenched state to a certain temperature below the charge ordering, facilitating relaxation to the charge order, which is more stable than the quenched metastable state. (B and C) Single-cycle operation of the nonvolatile switching. The time profiles of the resistivity and current are shown in (B) and (C), respectively. (D) Repetitive switching between the zero-resistance and nonzero-resistance states by the application of current pulses.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/4/10/eaau3489/DC1

    Supplementary Materials and Methods

    Fig. S1. Sample heating by a trapezoidal current-pulse application, followed by rapid cooling.

    Fig. S2. Measurements of the highest quenching rate achieved in the present experiments.

    Fig. S3. Simulation results of the quenching process for an IrTe2 thin plate on Si and PEN substrates.

    Fig. S4. Creation of persistent superconductivity by a current application in the IrTe2 thin plate #3.

    Fig. S5. Manipulation of the quenching rate by controlling the pulse fall time.

    Fig. S6. Annealing process of the quenched metastable state in the IrTe2 thin plate #3 on the Si substrate.

    Fig. S7. Magnetic field effects on the emergent superconductivity in the quenched metastable states.

  • Supplementary Materials

    This PDF file includes:

    • Supplementary Materials and Methods
    • Fig. S1. Sample heating by a trapezoidal current-pulse application, followed by rapid cooling.
    • Fig. S2. Measurements of the highest quenching rate achieved in the present experiments.
    • Fig. S3. Simulation results of the quenching process for an IrTe2 thin plate on Si and PEN substrates.
    • Fig. S4. Creation of persistent superconductivity by a current application in the IrTe2 thin plate #3.
    • Fig. S5. Manipulation of the quenching rate by controlling the pulse fall time.
    • Fig. S6. Annealing process of the quenched metastable state in the IrTe2 thin plate #3 on the Si substrate.
    • Fig. S7. Magnetic field effects on the emergent superconductivity in the quenched metastable states.

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