GdI2: A New Ferromagnetic Excitonic Solid?

The two-dimensional, colossal magnetoresistive system $\mathrm{Gd}{\mathrm{I}}_{2}$ develops an unusual metallic state below its ferromagnetic transition and becomes insulating at low temperatures. We argue that this geometrically frustrated, correlated poor metal is a possible candidate for a ferromagnetic excitonic liquid. The renormalized Fermi surface supports a further breaking of symmetry to a charge-ordered, excitonic solid ground state at lower temperatures via order by disorder mechanism. Several experimental predictions are made to investigate this unique orbitally correlated ground state.