Exciton condensation in an extended Falicov-Kimball model in the presence of orbital magnetic fields

E-ISSN： 1286-4854|116|5|57001-57001

ISSN： 0295-5075

Source： EPL (EUROPHYSICS LETTERS), Vol.116, Iss.5, 2017-01, pp. : 57001-57001

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Abstract

We investigate the exciton condensation in the presence of an external, perpendicular magnetic field in a two-dimensional extended spinless Falicov-Kimball model involving itinerant $(c)$ and localized $(f)$ electrons in the half-filled limit, using self-consistent, mean-field approximations. On tuning the orbital magnetic field the excitonic averages $\Delta_i =\langle c_i^\dagger f_i\rangle$ are affected in several ways: the external field usually suppresses the excitonic average but we find that it is also possible to enhance excitonic response at some values of the magnetic field. We further examine the effect of Coulomb interaction and the f-electron hopping on the condensation of excitons for some rational values of the applied magnetic fields. The interband Coulomb interaction enhances Δ exponentially and the effect is more pronounced for low hybridization. The strength of excitonic average drops when f-electrons have a dispersion. This trend is independent of the relative sign of the c- and f-electron hopping; although the excitonic response is different for different parity of the c- and f-electrons.