Detecting fractional Chern insulators through circular dichroism

Great efforts are currently devoted to the engineering of topological Bloch bands in cold atomic gas. Recent achievements in this direction as well as the possibility of tuning inter-particle interactions suggests that strongly-correlated states reminiscent of fractional quantum Hall (FQH) liquids, could soon be generated in these atomic systems. In this context where transport measurements are limited, identifying unambiguous signatures of FQH-like states constitutes a challenge on its own. Here, we demonstrate that the fractional nature of the quantized Hall conductance, a fundamental characteristic of FQH states, could be finely detected in ultracold gases through a circular-dichroic measurement, namely by measuring the energy absorbed by the atomic cloud upon a circular drive. We discuss how such measurements, which were recently implemented in the integer-QH regime, could indeed be performed to distinguish FQH-type states from competing states (such as charge density waves). Our scheme offers a practical and powerful tool for the detection of topological order in quantum engineered systems.