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Theory of Ferromagnetism in Doped Excitonic Condensates

E. Bascones·A. A. Burkov·A. H. MacDonald
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Abstract

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. In this paper 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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E. Bascones, A. A. Burkov, A. H. MacDonald. 2001-12-21. Theory of Ferromagnetism in Doped Excitonic Condensates. https://doi.org/10.1103/physrevlett.89.086401

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