Variational approach to self-trapped polarons and hopping transport – Vasilii Vasilchenko
Join us at the next Colloquium@T2P on
Variational approach to self-trapped polarons and hopping transport
Vasilii Vasilchenko
Institute of Condensed Matter and Nanosciences, Université catholique de Louvain, Belgium
Email: vasilii.vasilchenko@uclouvain.be
The talk will only be broadcast via Zoom:
https://hu-berlin.zoom-x.de/j/61666039212?pwd=9KFFDaHhj52P7YH1G1jqwsOlG2Ozux.1
Abstract:
Polarons are quasiparticles formed in condensed matter when charge carriers couple to the phonons of a system. Present in a wide range of materials with moderate to strong electron–phonon coupling, polaronic effects are responsible for various physical phenomena. These include renormalization of electronic bands, effective mass enhancement, and self-trapping of charge carriers. In the latter process, the charge becomes localized in the potential created by the self-induced polarization. As a result, transport may change from a band-like to the polaron hopping regime, in which transfer occurs through transition events between localization sites.
In this talk, I will discuss how self-trapped polarons and hopping transport can be approached from first principles. In particular, I will focus on the framework of variational polaron equations [1] and its extension for the calculation of minimal energy paths (MEPs) between localization sites. The ability to compute multiple polaronic states and MEPs connecting them on the polaron energy surface provides a way to estimate polaron hopping mobility within Marcus theory [2]. The capabilities of the formalism will be demonstrated using rutile TiO2, a semiconductor that exhibits electron polaron self-trapping and whose conductivity measurements display signatures of polaronic hopping [3].
References:
[1] V. Vasilchenko, M. Giantomassi, S. Poncé, X. Gonze, Phys. Rev. B, 112, 014314 (2025)
[2] N. Deskins, M. Dupuis, Phys. Rev. B, 75, 195212 (2007)
[3] S. X. Zhang et al., Phys. Rev. B 112, 014314 (2007)