Orbital-selective anisotropy and thermal anomaly in quasi-two-dimensional (, I) enabling directional thermoelectricity
Phys. Rev. B 112, 205201 – Published 3 November, 2025
DOI: https://doi.org/10.1103/1xvb-9crh
Abstract
Low lattice thermal conductivity and high power factor are essential for attaining superior thermoelectric performance. However, realizing their synergistic optimization in a single material poses a significant scientific challenge. In this work, we systematically investigate the thermoelectric transport properties of the quasi-two-dimensional materials ( = Br, I) by integrating first-principles calculations, anharmonic lattice dynamics, compressive sensing techniques, and Boltzmann transport theory. Considering strong quartic anharmonicity with self-energy corrections from bubble diagrams within the unified theory, and exhibit remarkably low of 0.35 and 0.26 W/mK, respectively, along the axis at 300 K. The strong anharmonicity in the system originates from the weak bonds induced by K atoms and the antibonding interactions between Pt and . At high temperatures, exhibits an anomalous increase with rising temperature due to the dominance of a glass-like thermal transport channel. Moreover, since the valence-band maximum and conduction-band minimum are dominated by orbitals along different directions, the electrical transport shows strong anisotropy under doping. At 900 K, optimally doped p-type achieves a of 2.06 along the axis, while n-type reaches 1.12 along the () axis, significantly outperforming conventional thermoelectric materials. These exceptional results demonstrate the outstanding potential of ( = Br, I) compounds for high-performance thermoelectric applications at elevated temperatures.
