Weak Ferromagnetism and Excitonic Condensates

Abstract

We investigate a model of excitonic ordering (i.e electron-hole pair condensation) appropriate for the divalent hexaborides. We show that the inclusion of imperfectly nested electron hole Fermi surfaces can lead to the formation of an undoped excitonic metal phase. In addition, we find that weak ferromagnetism with compensated moments arises as a result of gapless excitations. We study the effect of the low lying excitations on the density of states, Fermi surface topology and optical conductivity and compare to available experimental data.

10 Pages, 8 Figures, RevTeX

References in corpus (8)

• Excitonic ferromagnetism in the hexaborides
• CaB_6: a new semiconducting material for spin electronics
• Ferromagnetism and superstructure in Ca_{1-x}La_xB_6
• Electronic Fine Structure in the Electron-Hole Plasma in SrB6
• Excitonic order at strong-coupling: pseudo-spins, doping, and ferromagnetism
• Fermi Surface Measurements on the Low Carrier Density Ferromagnet Ca1-xLaxB6 and SrB6
• Ferromagnetism below the Stoner limit in La-doped SrB_6
• Impurity-induced Ferromagnetism in Doped Triplet Excitonic Insulator

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• Excitonic instability in two-dimensional degenerate semimetals
• Excitonic condensation in systems of strongly correlated electrons
• Excitonic pairing between nodal fermions
• Phase diagram of exciton condensate in doped two-band Hubbard model
• Theory of Ferromagnetism in Doped Excitonic Condensates
• Spin-Orbit Interactions in Bilayer Exciton-Condensate Ferromagnets
• Theory of Excitonic States in CaB6
• Theory of High \tc Ferromagnetism in $Sr{B}_6$ family: A case of Doped Spin-1 Mott insulator in a Valence Bond Solid Phase
• Excitonic Insulator and the Extended Falicov--Kimball Model Away from Half-Filling