Impact of quartic anharmonicity on lattice thermal transport in EuTiO3: A comparative theoretical and experimental investigation

We investigate the role of the quartic anharmonicity in the lattice dynamics and thermal transport of the cubic EuTiO3 by combining ab initio self-consistent phonon theory with compressive sensing techniques and experi-mental thermal conductivity determination measurement. The antiferromagnetic G-type magnetic structure is used to mimic the para-magnetic EuTiO3. We find that the strong quartic anharmonicity of oxygen atoms plays an important role in the phonon quasiparticles free from imaginary frequencies in EuTiO3 and causes the hardening of vibrational frequencies of soft modes. Based on these results, the lattice thermal transport prop-erties are predicted through the Boltzmann transport equation within the relaxation time approximation. The hardened modes thereby affect calculated lattice thermal conductivity significantly, resulting in an improved agreement with experimental results, including the deviation from kappa L proportional to T- 1 at high temperatures. The calculated thermal conductivity of 8.2 W/mK at 300 K matched the experimental value of 6.1 W/mK. When considering the boundary scattering, the calculated thermal conductivity is reduced to 6.9 W/mK at 300 K, which agrees better with the experiment.

Automated summary

We investigate the role of quartic anharmonicity in lattice dynamics and thermal transport of cubic EuTiO3 using ab initio self-consistent phonon theory, compressive sensing techniques, and experimental thermal conductivity measurement. We find that the strong quartic anharmonicity of oxygen atoms plays an important role in phonon quasiparticles free from imaginary frequencies in EuTiO3 and causes the hardening of vibrational frequencies of soft modes. The calculated thermal conductivity of 8.2 W/mK at 300 K matched the experimental value of 6.1 W/mK, and considering boundary scattering improved the agreement with the experiment to 6.9 W/mK at 300 K.