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Phase diagram of the excitonic insulator

B. Hülsen·F. X. Bronold·H. Fehske·K. Yonemitsu
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Abstract

Motivated by recent experiments, which give strong evidence for an excitonic insulating phase in $\rm TmSe_{0.45}Te_{0.55}$, we developed a scheme to quantitatively construct, for generic two-band models, the phase diagram of an excitonic insulator. As a first application of our approach, we calculated the phase diagram for an effective mass two-band model with long-range Coulomb interaction. The shielded potential approximation is used to derive a generalized gap equation controlling for positive (negative) energy gaps the transition from a semi-conducting (semi-metallic) phase to an insulating phase. Numerical results,obtained within the quasi-static approximation, show a steeple-like phase diagram in contrast to long-standing expectations.

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B. Hülsen, F. X. Bronold, H. Fehske, K. Yonemitsu. 2005-07-22. Phase diagram of the excitonic insulator. https://doi.org/10.1016/j.physb.2006.01.099

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