Research ArticleQUANTUM PHYSICS

Controlling the metal-to-insulator relaxation of the metastable hidden quantum state in 1T-TaS2

See allHide authors and affiliations

Science Advances  17 Jul 2015:
Vol. 1, no. 6, e1500168
DOI: 10.1126/sciadv.1500168
  • Fig. 1 Schematic description of the experiment and basic switching behavior.

    The unperturbed resistance is shown in the C state on cooling (blue data points) and on heating (red data points). The green curve shows the resistance in the H state after switching by a single 35-fs optical pulse above threshold. A schematic representation of the ordered phases C and NC is shown, with an indicated tentative ordering for the H state. The inset shows a schematic description of the experimental setup.

  • Fig. 2

    (A) Relaxation of the resistance R as a function of temperature after switching from the C to the H state. Before each measurement, the sample is heated above Tc2 and then cooled to the indicated temperature. After exposure to a single 35-fs laser pulse, the resistance is continuously measured as a function of time. (B) Fits to R(t) at different T using a stretched exponential function.

  • Fig. 3 Relaxation of the resistance after switching to the H state with electrical pulses.

    (A) R(t) at different temperatures after switching at t = 0. The inset shows a schematic diagram of the circuit. Before each measurement, the sample is heated above Tc2 and then cooled to the indicated temperature. After exposure to a 5-μs electrical pulse, the resistance is measured as a function of time. (B) Relaxation at a few selected temperatures with stretched exponential fits. The residual resistance RFitR obtained after subtracting the stretched exponential fit from the raw data shows distinct aperiodic oscillations with time.

  • Fig. 4 Relaxation rate 1/τH and the exponent as a function of 1/T.

    (A) A comparison of substrates with different tensile strain on a number of samples, also showing the sample-to-sample variation. The strain imposed by the sapphire, MgO, and quartz substrates at 50 K is 0.19, 0.13, and 0.03%, respectively (25). (B) A comparison for current and optical switching methods on sapphire. (C) Stretched exponent shows similar trend with T, irrespective of substrate or method of excitation. The legend shown in (C) applies to all three panels. The raw relaxation data for MgO and quartz substrates are shown in fig. S2A.

  • Fig. 5 Schematic diagram of the elementary relaxation process.

    (A) Thermal excitation of an electron (e) from itinerant band states at the Fermi level in the H state into the upper Hubbard band (UHB). LHB, lower Hubbard band; EF, Fermi energy. (B) Relaxation of one of the electrons. (C) Creation of a new polaron in the domain wall.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/1/6/e1500168/DC1

    Fig. S1. Temperature dependence of 20-nm-thick sample for different cooling-warming rates.

    Fig. S2. Temperature and fluence dependence of relaxation of the H state.

    Fig. S3. Schematic representation of the IC and H state relaxation in one dimension.

    Fig. S4. The numerous minima of the energy given by Eq. 1 form different metastable states of the system.

    Fig. S5. The phase shift and CDW density for a particular configuration of domain walls.

    Fig. S6. A comparison of fits with three different models to the data at 45 K described in the text.

    References (3846)

  • Supplementary Materials

    This PDF file includes:

    • Fig. S1. Temperature dependence of 20-nm-thick sample for different cooling-warming rates.
    • Fig. S2. Temperature and fluence dependence of relaxation of the H state.
    • Fig. S3. Schematic representation of the IC and H state relaxation in one dimension.
    • Fig. S4. The numerous minima of the energy given by Eq. 1 form different metastable states of the system.
    • Fig. S5. The phase shift and CDW density for a particular configuration of domain walls.
    • Fig. S6. A comparison of fits with three different models to the data at 45 K described in the text.
    • References (38–46)

    Download PDF

    Files in this Data Supplement:

Navigate This Article