Diamagnetism of an excitonic insulator

It has been shown that the diamagnetic susceptibility of an excitonic insulator exactly coincides with the Landau diamagnetic susceptibility for the normal (metal) state, i.e., above the point of the insulator-metal transition. The orbital part of the response to the magnetic field has been considered in the limit of the strong overlapping of electron-hole pairs. The perturbative calculations have been performed for absolute zero temperature.