The fascinating properties of IV-VI materials make them particularly suitable for thermoelectric applications. However, the microscopic origins of their good thermoelectric performance are not completely understood. Our research aims to uncover these mechanisms using parameter-free first principles approaches.
Recent studies showed that the soft optical phonons in PbTe and their strong anharmonic coupling with acoustic modes lead to the low thermal conductivity and high thermoelectric efficiency. The ultrafast diffuse X-ray experiments on photoexcited PbTe and our simulations show that the softening of these phonons stems from their strong coupling with the conduction and valance bands near the band gap.
M.P. Jiang, M. Trigo, I. Savić, S. Fahy, E. D. Murray, C. Bray, J. Clark, T. Henighan, M. Kozina, M. Chollet, J.M. Glownia, M.C. Hoffmann, D. Zhu, O. Delaire, A.F. May, B.C. Sales, A.M. Lindenberg, P. Zalden, T. Sato, R. Merlin, and D.A. Reis, "The Origin of Incipient Ferroelectricity in Lead Telluride", Nature Communications 7, 12291 (2016).