NEGF simulations for Quantum Transport in Carbon Nanotubes

During the summer of 2024, I undertook an internship at the Lawrence Berkeley National Laboratory (LBNL), working on simulating quantum transport in carbon nanotubes (CNTs). The Non-Equilibrium-Green’s Function (NEGF) formalism has become widely adopted in quantum transport simulations, which are crucial in developing an understanding of CNT operations. We built on ELEQTRONeX, a fast, parallelizable NEG framework. Our work has two major aspects: implementing fast methods for computationally complex self-energy calculations and adding external charge sources to allow for broader applications.

The existing ELEQTRONeX framework used an analytical self-energy solution, valid specifically for CNTs with basic lead configurations. To calculate more general self-energies, we used a tight-binding approximation, leading to an iterative and eigenfunction-based self-energy approach. Using randomly generated matrices, we showed that our methods are much more efficient than alternative direct inversions, allowing for faster and more complex NEGF geometries.

Motivated by discrepancies with experimental results, we also implemented point charges as external boundary conditions, which we demonstrated to have drastic impacts on our simulations.

My final report can read here and my poster can be found here .