Fig. 1: Band-gap-tuned semimetal-to-semiconductor transition in narrow band gap systems.
From: Anomalous excitonic phase diagram in band-gap-tuned Ta2Ni(Se,S)5
a Archetypal phase diagrams in indirect band gap controlled excitonic insulator (EI) across the semimetal-to-semiconductor transition. b Normal state electrical resistivity evolution with S-doping in Ta2Ni(Se,S)5. c Structure motif of quasi-1D Ta2Ni(Se,S)5 system below and above transition temperature Ts (upper panel). The lattice distortion in the monoclinic phase is exaggerated. Symbolic sketch of a minimal lattice model of the system used to describe the low-energy interactions in the system (lower panel). \({\epsilon }_{k}^{c}\) and \({\epsilon }_{k}^{v}\) are kinetic energies of conduction and valence electrons. ωq is the chain-shearing B2g phonon frequency. g is the interband electron-phonon coupling vertex. V is the electron-hole Coulomb interaction potential.
