Nonlocal effects in 1T-TaS2

Quantum materials possess a complex energy landscape and host many interesting physical phases. As a consequence of the competition of different phases or domains, many quantum materials exhibit nonlocality and nonlinearity in optical, thermal, electrical, and magnetic responses. Light-matter interactions have been used extensively as a probe to investigate the energy landscapes of quantum materials. In this report, we study the nonlocal effect in 1T-TaS2, a charge-density-wave material at room temperature. The light tunability in 1T-TaS2 has been hypothesized to relate to the interlayer couplings and different stacking mechanisms of 2D lattices, however, the nonlocal effect rising from the domain size has not been considered in the theory of optic responses for quantum materials, creating a gap between experimental results and theory. In this study, we characterize the momentum-dependent nonlocal factor for the dielectric function of 1T-TaS2. We model the domains as 2D arrays of dipoles and generate a nonlocal susceptibility based on effective medium theory. This step would be the first approximation toward modeling and understanding the competition of phases in many other strongly correlated systems.