Percolative Metal-Insulator Transition in LaMnO${}_3$

Abstract

We show that the pressure-induced metal-insulator transition (MIT) in LaMnO${}_3$ is fundamentally different from the Mott-Hubbard transition and is percolative in nature, with the measured resistivity obeying the percolation scaling laws. Using the Gutzwiller method to treat correlation effects in a model Hamiltonian that includes both Coulomb and Jahn-Teller interactions, we show, One, that the MIT is driven by a competition between electronic correlation and the electron-lattice interaction, an issue that has been long debated, and Two, that with compressed volume, the system has a tendency towards phase separation into insulating and metallic regions, consisting, respectively, of Jahn-Teller distorted and undistorted octahedra. This tendency manifests itself in a mixed phase of intermixed insulating and metallic regions in the experiment. Conduction in the mixed phase occurs by percolation and the MIT occurs when the metallic volume fraction, steadily increasing with pressure, exceeds the percolation threshold $v_c\approx 0.29$. Measured high-pressure resistivity follows the percolation scaling laws quite well, establishing the percolative nature of conduction, and the temperature dependence follows the Efros-Shklovskii variable-range hopping behavior for granular materials.

5 pages, 4 figures. This version contains more details on the fitting of the transport data (Fig. 5)

References in corpus (5)

• Pressure-induced metal-insulator transition in LaMnO3 is not of Mott-Hubbard type
• Coulomb Interactions and Nanoscale Electronic Inhomogeneities in Manganites
• Theory of hopping conduction in arrays of doped semiconductor nanocrystals
• Bandwidth-driven nature of the pressure-induced metal state of LaMnO3
• Gutzwiller Variational Method for Intersite Coulomb Interactions: The Spinless Fermion Model in One Dimension

Cited by in corpus (4)

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• Charge density functional plus $U$ theory of LaMnO${}_3$: Phase diagram, electronic structure, and magnetic interaction
• The 2D percolation transition at finite temperature: The phase boundary for in-plane ferromagnetism in $\approx$2 ML Fe/W(110) films
• Geometric Percolation Threshold Defines Half-Metallic Window in Vacancy-Doped Titanium disulfides