Chemical partitioning of electronic transport and four-phonon limited heat conduction in monolayers
Phys. Rev. Materials 10, 105201 – Published 13 October, 2026
DOI: https://doi.org/10.1103/tfck-9l46
Abstract
Identifying high-performance thermoelectrics in chemically related two-dimensional materials requires understanding how different sublattices separately regulate electronic transport, phonon softening, and anharmonic heat conduction. Here, we use monolayers as a model material family to establish such a chemically resolved design principle. By combining first-principles stability analysis, carrier-transport calculations, and lattice thermal conductivity calculations including both three- and four-phonon scattering, we systematically investigate 30 monolayers with , Y, Al-In and -Te, Cl-I. The dynamically stable semiconducting members are mainly concentrated in the Al-, Ga-, and In-based chalcogenides, defining a selective thermoelectric stability window rather than a random set of candidates. We find that the -site cation primarily controls the electronic transport through band-edge dispersion and valley convergence, whereas the -site anion predominantly governs lattice heat conduction by tuning phonon softening, group velocity, and higher-order anharmonic scattering. This chemical partitioning leads to a favorable balance in , which reaches a peak of 2.75 at 900 K. More importantly, explicit four-phonon calculations show that conventional three-phonon treatments systematically overestimate the lattice thermal conductivity of representative high-performance members by 37–53%, demonstrating that four-phonon scattering is not a minor correction but a necessary criterion for reliable thermoelectric assessment in this family. These results identify , and as the high-performance region of the family and establish a transferable materials-physics framework linking sublattice chemistry, electronic transport, and four-phonon-limited heat conduction in two-dimensional thermoelectrics.
