Figure 2
(a) Electronic dispersion of the Landau subbands according to ref. 19 at B < B 0, giving rise to a small overlap (E g < 0) between the minority-spin electron (\({\varepsilon }_{{\rm{\min }}}^{{\rm{e}}}\)) and hole (\({\varepsilon }_{{\rm{\min }}}^{{\rm{h}}}\)) Landau subbands (depicted in black). The majority-spin bands (\({\varepsilon }_{{\rm{maj}}}^{{\rm{e}}}\)) and (\({\varepsilon }_{{\rm{maj}}}^{{\rm{h}}}\)) are depicted in grey. (b) Electronic dispersion at B > B 0, giving rise to a small gap (E g > 0) between the minority-spin electron and hole bands. (c) Schematic dispersion for a spin-triplet excitonic insulator phase (a spin-density-wave for weak coupling that doubles the c-axis unit cell) for E g < 0. The folded dispersion is calculated from the anticrossing of the translated bands with the exciton gap function Δ using \({\varepsilon }_{{\rm{\min }}\,,{\rm{maj}}}^{\pm }=\frac{1}{2}[{\varepsilon }_{{\rm{\min }}\,,{\rm{maj}}}^{{\rm{e}}}({k}_{z})+{\varepsilon }_{{\rm{\min }}\,,{\rm{maj}}}^{{\rm{h}}}({k}_{z}+{Q}_{z})]\pm \sqrt{\frac{1}{4}{[{\varepsilon }_{{\rm{\min }},{\rm{maj}}}^{{\rm{e}}}({k}_{z})-{\varepsilon }_{{\rm{\min }},{\rm{maj}}}^{{\rm{h}}}({k}_{z}+{Q}_{z})]}^{2}+{{\rm{\Delta }}}^{2}}\). (d) Same as (c) but for E g > 0.
