LMS Seminars

Polarons and non-polarons from first principles

by Prof. Matthieu Verstraete (Utrecht University)




Electrons and holes in crystals interact with the atomic lattice and are “dressed” by phonons. The resulting quasiparticles (polarons) can be more or less massive, localized, or mobile. The standard models for polarons by Fröhlich Holstein and others have held up for over 60 years: in the present talk we explore some of their limits. We quantify the applicability of the widely used Fröhlich model for large polarons [1] in a high-throughput test [2] of its hypotheses, showing its broad range of applicability, and identifying dozens of strong coupling cases where it should break down.

A core tenet of Fröhlich polarons is that they interact through dielectric polarization: we have also examined from first principles what happens in a-polar crystals [3], which host “non-polarons”, a term first coined by Emin[4]. We had expected that in diamond quadrupoles would “take over” given the bonding geometry and charge distribution, but in fact much more localized fields dominate the polaronic response, and provide characteristic spectral signatures.

[1] H. Fröhlich “Interaction of electrons with lattice vibrations” Proc Roy Soc London A, 1952 vol 215, p. 291
[2] P. Melo et al. “High-throughput analysis of Frohlich-type polaron models” npj Computational Materials, 2023 vol 9, p. 147
[3], J.C. de Abreu, et al.  “Spectroscopic signatures of nonpolarons” Phys Chem Chem Phys 2022 vol 24, p. 12580
[4]. D. Emin and M.-N. Bussac “Disorder-induced small-polaron formation”, Phys Rev B 1994 vol. 49, p. 14290

Organized by

Laboratory for Materials Simulations LMS

Dr. Giovanni Pizzi & Dr. Flaviano Dos Santos