Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

Non-Fermi liquid behavior in La$_3$Ni$_2$O$_7$ thin films under hydrostatic pressure

Deepak Kumar, Jared Z. Dans, Keenan E. Avers, Ryan Paxson, Ichiro Takeuchi, Johnpierre Paglione

Abstract

The discovery of superconductivity in bilayer nickel-oxides has revived an intense effort to understand the potential of high-temperature superconductivity in these materials and their relation to cuprate superconductors. In this work, we investigate the growth and properties of bilayer La$_3$Ni$_2$O$_7$ thin films as a function of substrate, oxygen treatment and applied pressure in order to study the evolution of transport properties. We report epitaxial growth of La$_3$Ni$_2$O$_7$ thin films on LaAlO$_3$ (LAO) (001) and SrLaAlO$_4$ (SLAO) (001) substrates, and the effects of ex-situ annealing in a high pressure furnace under an oxygen-rich environment. Transport measurements show that the La$_3$Ni$_2$O$_7$ thin films on LAO(001) exhibit Fermi liquid-like metallic behavior with a slight Kondo-like upturn at low temperatures, which evolves with the application of modest hydrostatic pressures toward non-Fermi liquid behavior with a temperature dependence of resistance approaching $\sim$ T$^{1.4}$ at 1.41 GPa. The ability to tune the normal state resistivity of La$_3$Ni$_2$O$_7$ films to display non-Fermi liquid behavior under such a modest hydrostatic pressure range - only 6 - 8 % of that typically applied via diamond anvil cell (DAC) in La$_3$Ni$_2$O$_7$ single crystals to achieve comparable effects - is both noteworthy and unexpected. These findings imply the strong tunability of La$_3$Ni$_2$O$_7$ in thin film form and the likely proximity of a strongly fluctuating ordered state leading to non-Fermi liquid behavior under even modest applied pressures.

Non-Fermi liquid behavior in La$_3$Ni$_2$O$_7$ thin films under hydrostatic pressure

Abstract

The discovery of superconductivity in bilayer nickel-oxides has revived an intense effort to understand the potential of high-temperature superconductivity in these materials and their relation to cuprate superconductors. In this work, we investigate the growth and properties of bilayer LaNiO thin films as a function of substrate, oxygen treatment and applied pressure in order to study the evolution of transport properties. We report epitaxial growth of LaNiO thin films on LaAlO (LAO) (001) and SrLaAlO (SLAO) (001) substrates, and the effects of ex-situ annealing in a high pressure furnace under an oxygen-rich environment. Transport measurements show that the LaNiO thin films on LAO(001) exhibit Fermi liquid-like metallic behavior with a slight Kondo-like upturn at low temperatures, which evolves with the application of modest hydrostatic pressures toward non-Fermi liquid behavior with a temperature dependence of resistance approaching T at 1.41 GPa. The ability to tune the normal state resistivity of LaNiO films to display non-Fermi liquid behavior under such a modest hydrostatic pressure range - only 6 - 8 % of that typically applied via diamond anvil cell (DAC) in LaNiO single crystals to achieve comparable effects - is both noteworthy and unexpected. These findings imply the strong tunability of LaNiO in thin film form and the likely proximity of a strongly fluctuating ordered state leading to non-Fermi liquid behavior under even modest applied pressures.

Paper Structure

This paper contains 5 sections, 4 figures.

Table of Contents

  1. Introduction
  2. Experimental
  3. Results and discussion
  4. Conclusions
  5. acknowledgments

Figures (4)

  • Figure 1: (a) Schematic representation of lattice mismatch between LNO$_{327}$ and various oxide substrates. (b) Reflection High Energy Electron Diffraction (RHEED) patterns for the bare SLAO(001) substrate (left panel) and that of the film hetrostructure (right panel). (c),(d) X-ray Diffraction (XRD) $\theta$-2$\theta$ scans for LNO$_{327}$ films on SLAO(001) and LAO(001) substrates, respectively. The (00l)$_F$ diffraction peaks belong to the LNO$_{327}$ thin film.
  • Figure 2: (a) Resistivity vs. temperature plots for the as-grown LNO$_{327}$ film on LAO(001) and the corresponding scans for the annealed films in in-situ PLD (at 300 torr, 650 $^{\circ}$C) and in high pressure furnace (PF) (at 15 bar, 650 $^{\circ}$C) for 18 hrs. Temperature dependence of resistance for (b) topotactically reduced LNO$_{327}$ thin film on LAO substrate, (c) pristine and annealed LNO$_{327}$ films on the SLAO(001) substrate. Annealing of films on SLAO(001) substrate was performed in presssure furnace at 15 bar, 650 $^{\circ}$C for 18 hrs.
  • Figure 3: Hall effect measurements for LNO$_{327}$ films on the YAO(110) and LAO(001) substrates; (a) Sheet resistance (b) Hall coefficient (R$_H$), (c) carrier concentration (n) plotted as a function of temperature for the LNO$_{327}$ film on YAO(110) substrate.(d) Sheet resistance (e) Hall coefficient (f) carrier concentration plotted with temperature for LNO$_{327}$ film on the LAO(001) substrate. The dashed line shows transition around 117 K, and is only guide to the eyes.
  • Figure 4: (a) Resistance vs temperature scans for the LNO$_{327}$ film on LAO(001) substrate under pressure. (b) Power law fits to the data at low temperature. The symbols represent data points and the black lines represent the fits. The $T$-dependence changes from $T$$^2$ at 0.53 GPa to $T$$^{1.4}$ at 1.41 GPa.