  In strongly correlated quantum materials, electrons behave in ways that often
extend beyond the confines of conventional Fermi-liquid theory. Interesting
results include the observation of low-temperature metallic behavior in systems
that are highly resistive. Here we provide an overview of experiments in which
insulators exhibit characteristics of a metal such as the Shubnikov de Haas
like quantum oscillations, focusing on recent findings in the correlated
insulating states of two-dimensional WTe2. We discuss the status of current
research, clarify the debates and challenges in interpreting the experiments,
rule out extrinsic explanations and discuss promising future directions.
