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MON: Monday Contributed Sessions

MON 22: Quantum Transport II

MON 22.1: Talk

Monday, September 8, 2025, 16:30–16:45, ZHG104

Ultralow Lattice Thermal Conductivity and Colossal Thermoelectric Figure of Merit of the Room Temperature Antiferromagnet CsMnBi — •shubham Rakesh Singh¹, Nirpendra Singh², and Udo Schwingenschlögl¹ — ¹Physical Science and Engineering Division (PSE), King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia — ²Department of Physics, Khalifa University of Science and Technology, Abu Dhabi-127788, United Arab Emirates

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 a indirect bandgap of 0.9 eV and to realize C-type antiferromagnetism, which is energetically favorable by 187 meV 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 Wm⁻¹K⁻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.

Keywords: thermoelectric; phonon-phonon scattering; attice thermal conductivity; antiferromagnetism; spin orbit coupling