Researchers at Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR), Bengaluru, have discovered an unusual wave-like heat transport regime in a newly studied copper chalcogenide material called thallium copper selenide (TlCu5Se3) that could enable efficient conversion of waste heat to electricity through thermoelectric energy conversion. The breakthrough has potential applications in power plants, cement industries, steel plants, automobiles, data centers, and battery heat management systems.
The material achieves ultralow lattice thermal conductivity through a complex crystalline framework that restricts copper atom motion while maintaining structural stability. Unlike conventional materials where heat is transported by particle-like phonons, TlCu5Se3 exhibits wave-like coherence between different vibrational modes due to strong anharmonicity and confined dynamic disorder of the copper sublattice. This unconventional heat transport mechanism, combined with favorable electronic transport properties, results in a thermoelectric figure of merit (zT) of 1.7, which is among the highest values reported for pristine ternary chalcogenides.
The research team, led by Prof. Kanishka Biswas with Ph.D. students Ms. Sayantoni Choudhury and Dr. Animesh Bhui from the New Chemistry Unit at JNCASR, collaborated with Prof. Umesh V. Waghmare and Dr. Prasad V. Matukumilli from the Theoretical Sciences Unit to perform advanced first-principles theoretical calculations and molecular dynamics simulations. These simulations revealed that copper atoms exhibit localized dynamic disorder rather than long-range, liquid-like diffusion, which acts as a source of strong lattice anharmonicity. The compound crystallizes in a tetragonal structure forming a complex three-dimensional cloverleaf knot-like framework with open channels along the crystallographic c-axis.
The research was published in the journal Science Advances (DOI:10.1126/sciadv.aeh9096) and represents a significant advancement in thermal management technologies, demonstrating how structural complexity and confined ion dynamics can lead to unconventional mechanisms for high-performance thermoelectric energy conversion.