Energy flow in laser-excited hBN-graphene heterostructures*

Inter-material correlations of electrons and phonons in vdW heterostructures, like hBN-graphene open interaction and energy diffusion channels that are not present in either of the single materials. Recent research showed, e.g., out-of-plane heat transfer by electron-hyperbolic phonon coupling [1] or ultrafast relaxation of hot phonons [2]. Here, we studied how laser-deposited energy is distributed within and between the layers of the heterostructure. Therefore, we performed ab initio calculations of mono-layer hBN-graphene and many-layer hBN-graphite heterostructures excited by femtosecond-laser pulses with a central wavelength of 800 nm. Note that hBN is transparent for that wavelength: it does not absorb laser-pulse energy, whereas graphene does. By comparing our simulation results to our experimentally obtained time-resolved electron diffraction data we gain insights on the energy flow from excited graphene to the connected hBN layer within a 2D heterostructure on an atomistic level and ultrashort timescale.

[1] Klaas-Jan Tielrooj, et al., Nature Nanotechnology 13, 41–46 (2018)

[2] Dheeraj Golla, et al., APL Mat. 5, 056101 (2017)