Condensed Matter Physics Seminar: Ivana Savic

Abstract:

Thermoelectric materials allow for reversible conversion of heat to electricity, which makes them attractive for energy harvesting applications. It is very challenging to create materials that enable efficient thermoelectric energy conversion due to conflicting requirements for relevant material properties (i.e. high electrical conductivity, high Seebeck coefficient and low thermal conductivity). All these properties are governed by electron-phonon and phonon-phonon interactions, which are very difficult to characterise. However, recent developments in ultrafast X-ray and ARPES measurements, as well as first principles computational methods, have enabled substantial progress on that front. In this talk, I will present our efforts to understand electron-phonon and phonon-phonon interactions in some of the best performing thermoelectric materials, PbTe and Bi2Te3, combining ultrafast measurements and first principles calculations. I will show that electron-phonon coupling involving electronic states near the band edges lead to strong phonon-phonon interactions and lattice instability in PbTe [1], which are critical for its excellent thermoelectric performance. I will also show that the electronic surface states of the topological insulator Bi2Te3 couple with different types of photoexcited phonons and discuss the potential implications on thermoelectric properties [2].

[1] M. P. Jiang et al., Nat. Commun. 7, 12291 (2016)

[2] J. A. Sobota et al., Phys. Rev. B 107, 014307 (2023)