Research ArticleCONDENSED MATTER PHYSICS

Tuning bad metal and non-Fermi liquid behavior in a Mott material: Rare-earth nickelate thin films

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Science Advances  06 Nov 2015:
Vol. 1, no. 10, e1500797
DOI: 10.1126/sciadv.1500797
  • Fig. 1 MITs and temperature dependence of resistivity.

    The graphs show the resistivity as a function of temperature for NdNiO3 (NNO) films with thicknesses ranging between 4 and 15 u.c. on six different substrates [YAO, YAlO3; LAO, LaAlO3; NGO, NdGaO3; LSAT, (LaAlO3)0.3(Sr2AlTaO6)0.7; STO, SrTiO3; DSO, DyScO3]. Each panel corresponds to a different substrate, with the corresponding epitaxial strain noted in parentheses. Solid lines are experimental data and dashed lines are fits using Eqs. 1 and 2. The horizontal solid line is the Mott-Ioffe-Regel limit according to Eq. 3.

  • Fig. 2 Resistance saturation and NFL behavior in the metallic state.

    (A) Temperature derivative of the resistivity as a function of temperature (8-u.c. film on LaAlO3). The negative slope at higher temperatures is a manifestation of ρSAT in Eq. 2, and the dashed blue curve is a fit to Eq. 2 and Embedded Image. The downturn at lower temperatures represents the MIT. The red and orange dashed curves are fits to Eq. 1, with Embedded Image and 1, respectively, which cannot describe the data. (Inset) A plot of ρNFL (extracted from the fit to Eq. 2) as a function of Embedded Image. (B) Extracted exponents n for different film thicknesses (tNNO) and substrates [YAO, YAlO3; LAO, LaAlO3; NGO, NdGaO3; LSAT, (LaAlO3)0.3(Sr2AlTaO6)0.7; STO, SrTiO3]. (C) ρSAT and ρ(0) as a function of tNNO for the different substrates. Dashed lines are extrapolated polynomial fits to ρ(0) used to determine the thicknesses corresponding to ρSAT = ρ(0) for the different substrates. (D) ρSAT, ρ0, and ρ(0) as a function of the in-plane epitaxial strain (εxx) for the 15-u.c. films. The dashed line represents the Mott-Ioffe-Regel limit according to Eq. 3.

  • Fig. 3 Strain-thickness phase diagram.

    (A) Prototypes for the four basic behaviors seen in the ρ-T curves shown in Fig. 1. (B) Phase diagram for εxx versus tNNO. The boundaries are drawn between the four basic behaviors shown in (A). Each point indicates a transport curve in Fig. 1. Black diamonds represent predictions for MIT based on ρ(0) = ρSAT.

  • Fig. 4 Strain-temperature phase diagram.

    Each panel corresponds to a different NdNiO3 (NNO) thickness. Symbols indicate MIT temperatures measured for films under different strains. The colors of the regions correspond to those in Fig. 3, and boundaries are drawn to be consistent with Fig. 3. YAO, YAlO3; LAO, LaAlO3; NGO, NdGaO3; LSAT, (LaAlO3)0.3(Sr2AlTaO6)0.7; STO, SrTiO3; DSO, DyScO3.

  • Fig. 5 Saturation resistance and orbital splitting as a function of strain.

    (A) Schematic showing the lifting of eg orbital degeneracy in NdNiO3. (B) Magnitude of the calculated orbital splitting |Δ| in NdNiO3 and measured ρSAT as a function of εxx. (Inset) Correlation between the two quantities.

Supplementary Materials

  • Supplementary Materials

    This PDF file includes:

    • Fig. S1. Resistivity as a function of temperature.
    • Fig. S2. ρ-T data for LaNiO3.
    • Fig. S3. Saturation resistivity and NFL behavior in LaNiO3.
    • Fig. S4. Electron-electron scattering coefficient A.

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