First-principles calculations reveal ultralow thermal conductivity of 0.07 W/m·K and a thermoelectric figure of merit of 2.2 in the antiferromagnetic material CsMnBi, indicating strong potential for energy applications.
We study the experimentally synthesized layered material CsMnBi using first-principles calculations and the linearized electron and phonon Boltzmann transport equations. CsMnBi is found to be a semiconductor with an indirect bandgap of 0.76 eV and to realize C-type antiferromagnetism, which is energetically favorable by 0.19 eV per formula unit over ferromagnetism. Energetical overlap between the acoustic and low-frequency optical phonon modes enhances the phonon-phonon scattering. Combined with low group velocities and high lattice anharmonicity this results in an ultralow lattice thermal conductivity of 0.07 W m-1 K-1 at 300 K. A high thermoelectric figure of merit of 2.2 (1.7) is achieved at 300 K at a hole (electron) density of 6.0 × 1018 (1.0 × 1018) cm-3.
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Singh et al. (2025) studied this question.
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