Coupled Electro-Thermal Transport in Two-Dimensional Materials and Heterostructures

Research by Zlatan Aksamija and Sylvester Makumi

At the heart of this project is the development and applications of a simulation tool to solve the coupled Boltzmann transport equations for electrons and phonons in two-dimensional (2D) materials. Simulating thermal dissipation inside 2D nanostructures requires a two-way coupled treatment of electrons and heat, the latter being transported by phonons. Computing electron-phonon coupling from first principles and solving the electron and phonon Boltzmann transport equations using ab initio inputs has now reached full maturity. However, there is a critical need for a platform that will enable studying non-isothermal transport, where electron and phonon populations are simulated concurrently so that phonons generated by electron-phonon coupling are tracked and their distribution/temperature fed back into electron transport and vice versa. To address this need, we are developing a code for two-way coupled electron-phonon Boltzmann transport simulation of 2D materials and heterostructures. The code will build on first-principles data computed using Density Functional Theory to enable predictive simulation for realistic applications. So far, we have studied the impact of atomic-scale roughness at the interface between a 2D sheet and a 3D substrate on the heat transfer across that interface, and the ability to tune the interface thermal conductance by applying an external voltage to exert pressure on the soft van der Waals bonds that hold the interface together. Our results show that thermal conductance can be enhanced by a combination of atomic-scale roughness and electrostatic pressure, which will enable further enhancements in the thermal management of nanoelectronic devices built from 2D materials.

In our work, we rely on fundamental materials properties computed from first principles using Density Functional Theory, as implemented in the code VASP. To model multilayered materials, we employ so-called supercells that have tens to hundreds of atoms and require significant computational resources and storage for the results. CHPC resources enable such calculations and accelerate the time to solution. The DFT code VASP is parallelized, which allows us to run heavy calculations across multiple compute nodes, taking advantage of both the added "number crunching" power and memory, which enable more accurate simulations.

Attribution: This content was provided by the researchers. CHPC staff made minor edits to style.