GdI2: A new ferromagnetic excitonic solid?

Abstract

The two-dimensional, colossal magnetoresistive system GdI2 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. © 2008 The American Physical Society.