Master's Defense: Eva Lopez Rojo

Charge bond order in kagome metals

The vanadium kagome metals AV3Sb5 have been the subject of extensive research since their synthesis in 2019, both theoretically and experimentally. Due to the unique geometry of the kagome layer, their electronic structures exhibit flat bands, van Hove singularities and Dirac cones, making them an excellent platform for investigating the interplay between correlation effects, geometric frustration, and topology. Notably, all three compounds are found to enter a charge density wave phase at high temperature, which breaks translational symmetry generating a 2x2x2 supercell. Additionally, this phase is also reported to break time reversal symmetry and exhibit a giant anomalous Hall effect despite the absence of long-range magnetic order. The focus of this thesis is to study the emergence of said charge density wave phase from electronic interactions. A nearest-neighbour Hubbard model on the kagome lattice is presented, which is decoupled using a Hubbard-Stratonovich transformation. Within mean-field theory, the Ginzburg-Landau free energy is analyzed, determining the potential order parameters of the symmetry-broken phase.