Disappearing Charge Density Wave in Kagome Metal FeGe

Kagome metals provide means of probing new correlated quantum phenomena due to the naturally incorporated linear dispersion, flat bands, and van Hove singularities of their bandstructures. Among these quantum phenomena is the charge density wave (CDW), or the temporary distortion of the lattice structure due to the motion of correlated electrons through the material. CDWs are thought to lower the Fermi energy of the compound, creating an energy gap allowing for behavior akin to superconductivity, nonlinear transport, or other correlated electron motion. Kagome metal FeGe is hypothesized to have a CDW that occurs around 100 K, but the exact mechanism of this phenomenon is unknown. We performed thermoelectric measurements on FeGe with magnetic field dependance up to 14 T, not only proving its presence, but also evidencing its disappearance under the right annealing conditions. We performed thermoelectric measurements on 3 FeGe samples: without annealing, annealed for 96 hours at 320 C, and annealed for 96 hours at 560 C. By measuring the Nernst and Seebeck effects in this Kagome compound, we were able to provide evidence of multiple phase transitions, both confirming the presence of a CDW in FeGe, and demonstrating its disappearance given sufficient annealing.