Through a combined theoretical and experimental effort, we uncover a yet unidentified mechanism that strengthens considerably electron-phonon coupling in materials where electron accumulation leads to population of multiple valleys. Taking atomically-thin transition-metal dichalcogenides as prototypical examples, we establish that the mechanism results from a phonon-induced out-of-phase energy shift of the different valleys, which causes inter-valley charge transfer and reduces the effectiveness of electrostatic screening, thus enhancing electron-phonon interactions. The effect is physically robust, it can play a role in many materials and phenomena, as we illustrate by discussing experimental evidence for its relevance in the occurrence of superconductivity. (short abstract due to size limitations - full abstract in the manuscript)
@article{arxiv.1901.08012,
title = {Enhanced electron-phonon interaction in multi-valley materials},
author = {Evgeniy Ponomarev and Thibault Sohier and Marco Gibertini and Helmuth Berger and Nicola Marzari and Nicolas Ubrig and Alberto F. Morpurgo},
journal= {arXiv preprint arXiv:1901.08012},
year = {2019}
}