Electron-Induced Non-Equilibrium Phonon Dynamics in Two-Dimensional Materials

Non-equilibrium energy transfer between hot electrons and phonons plays an important role in the design and operation of photovoltaic and nanoelectronic devices. In this talk, I will show how high energy electrons in two-dimensional (2D) materials are conducive to non-equilibrium phonon distribution using a newly developed first-principles simulation framework to model coupled time-evolution of electron and phonon occupations. Our method [1] accounts for electron-phonon and phonon-phonon interactions on an equal footing. For materials such as graphene, silicene, germanene, and transition metal dichalcogenides, we find that electron-induced heating strongly differs from classical heat, inducing a long-lasting, non-equilibrium distribution between in-plane and out-of-plane vibrational modes. We propose a general, dimensionless material descriptor accounting for field gradients and crystal symmetry able to characterize the nature of electronically-driven phonon distributions in two dimensional materials.

[1] Sadasivam, Chan, Darancet, Phys. Rev. Lett., 119, 136602 (2017)