Probing correlated states with plasmons

Understanding the nature of strongly correlated states in flat-band materials (such as moire heterostructures) is at the forefront of both experimental and theoretical pursuits. While magnetotransport, scanning probe, and optical techniques are often very successful in investigating the properties of the underlying order, the exact nature of the ground state often remains unknown. Here, we propose to leverage strong light-matter coupling present in the flat-band systems to gain insight through dynamical dielectric response into the structure of the many-body ground state. We argue that because of the enlargement of the effective lattice of the system arising from correlations, conventional long-range plasmon becomes folded to yield a multiband plasmon spectrum. We detail several mechanisms through which the structure of the plasmon spectrum and that of the dynamical dielectric response is susceptible to the underlying order, revealing valued insights such as the interaction -driven band gaps, spin-structure, and the order periodicity.

Automated summary

Understanding strongly correlated states in flat-band materials is a major focus for both experimental and theoretical research. While various techniques have been successful in studying the properties of the order, the exact nature of the ground state remains unknown. In this study, we propose using strong light-matter coupling in flat-band systems to gain insight into the many-body ground state through dynamical dielectric response. We demonstrate that the plasmon spectrum and dynamical dielectric response are susceptible to the underlying order, providing valuable insights into interaction-driven band gaps, spin structure, and order periodicity.