Theory of ferromagnetism in doped excitonic condensates.


Nesting in a semimetal can lead to an excitonic-insulator state with spontaneous coherence between conduction and valence bands and a gap for charged excitations. We present a theory of the ferromagnetic state that occurs when the density of electrons in the conduction band and holes in the valence band differ. We find an unexpectedly rich doping-field phase diagram and an unusual collective excitation spectrum that includes two gapless collective modes. We predict regions of doping and external field in which phase-separated condensates of electrons and holes with parallel spins and opposing spins coexist.

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@article{Bscones2002TheoryOF, title={Theory of ferromagnetism in doped excitonic condensates.}, author={Esther B{\'a}scones and Anton A. Burkov and Allan H. MacDonald}, journal={Physical review letters}, year={2002}, volume={89 8}, pages={086401} }