More than half of industrial waste heat is low-temperature, below about 500 kelvin, and most of it is simply lost: existing thermoelectric materials convert it too inefficiently for widespread use. Researchers in Udo Schwingenschloegl's group at KAUST, with doctoral student Shubham Singh as first author, have identified an unexpected class of candidates in altermagnets, materials with spin-split electronic bands but zero net magnetisation, studied until now mainly for their exotic magnetism.
Using first-principles simulations combined with the phonon Boltzmann transport equation, the team modelled the monolayer vanadium oxyselenide V2Se2O and its Janus derivative V2SeTeO, in which tellurium replaces every other selenium atom and breaks the structure's symmetry. The heavier tellurium slows phonon group velocities and boosts phonon-phonon scattering, cutting lattice thermal conductivity by a factor of nineteen while leaving electronic transport favourable.
The result, published in Materials Science and Engineering R: Reports, is a predicted thermoelectric figure of merit of 2.7 at 500 kelvin, exceeding commercial lead- and bismuth-based materials in the low-temperature range where recovery matters most. The findings are theoretical, and the team's next steps are to screen other Janus altermagnets and partner with experimental groups to grow the monolayers and assemble working thermoelectric modules.