Anomalous thermal transport in Li₂Te by high-pressure enhanced four-phonon scattering

High pressure typically enhances thermal conductivity by strengthening atomic interactions. However, PdS has recently been reported to exhibit an unusual pressure-induced suppression of thermal conductivity, which in turn leads to a remarkable enhancement in its thermoelectric performance at high pressure. These insights motivate the search for additional materials that exhibit anomalous thermal-transport behavior under high pressure. Here, we find that hydrostatic pressure induces an anomalous change in lattice thermal conductivity (κ_l) in antifluorite structure Li₂Te by density-functional theory and phonon Boltzmann-transport calculations. The lattice thermal conductivity decreases monotonically under pressure, dropping by 72% to 1.99 W m⁻¹K⁻¹ at 40 GPa compared to ambient conditions. This anomalous behavior arises from the broadened acoustic branches and the enlarged acoustic-optical (a-o) phonon gap under high pressure, which together intensify phonon scattering. The enhanced anharmonicity under pressure is evidenced by both flattened frozen-phonon potentials and enhanced Grüneisen parameters. This work establishes Li₂Te as a prototypical system for pressure-mediated thermal-transport tuning and highlights phonon scattering as a critical design parameter for engineering materials.