Emergent phenomena in strained graphene nanostructures : advanced numerical simulations of electronic properties and the pseudo-magnetic field of graphene-based strain-textured nanostructures and superlattices

Abstract

This thesis investigates how controlled deformations and heterostructures in graphene can be exploited for electronic applications by combining molecular dynamics (MD) simulations with tight-binding (TB) calculations. First, the pseudo-vector potential in strained graphene is analyzed by comparing continuum elasticity and atomistic MD approaches. While continuum models capture only acoustic displacements, MD reveals significant contributions from optical modes, which effectively screen the pseudo-gauge field and substantially reduce predicted pseudo-magnetic fields. Next, indentation-induced doping in graphene on a Cu(111) substrate is studied. TB calculations based on MD-relaxed structures reproduce experimentally observed Fermi energy shifts of up to 0.3 eV and attribute them to resonant states arising from local bond defects. Moving to larger scales, graphene nanobubbles on Pt(111) are modeled by combining MD simulations with scanning tunneling microscopy data. The resulting electronic structure shows quasi-confinement due to both electrostatic and pseudo-magnetic effects, without forming pseudo-Landau levels inside the bubble, while such states emerge outside within a limited spatial range. Finally, moiré engineering in graphene-hBN heterostructures is explored. Relative layer alignment and electrostatic gating enable tuning of primary and secondary Dirac point gaps and the formation of flat bands. We further show that this mechanism underlies the observed negative differential resistance and subsequent single-photon emission in identical experimental setups, providing a platform for future optoelectronic applications.