Ab Initio Path Integral Monte Carlo Study of the 2D Uniform Electron Liquid at Finite Temperatures: Structural Properties, Density Response and Roton‐Type Excitation

We present extensive ab initio path integral Monte Carlo (PIMC) simulations of the two‐dimensional uniform electron gas (2DEG), covering a broad range of density parameters and temperatures . This allows us to analyze various structural, linear density response and spectral properties. We find clear evidence of a roton‐type feature in the dynamic structure factor at strong coupling and intermediate wavenumbers. We also benchmark novel dielectric theory implementations for the 2DEG [Kalkavouras et al. arXiv:2601.14989] for structural and spectral properties across the liquid phase diagram. The PIMC results can be used to benchmark existing theories and approximations, and guide the development of new methodologies.