Effects of Fermion Flavor on Excitonic Condensation in Double Layer Systems

We perform fermionic path integral quantum Monte Carlo (PIMC) simulations to study the physical properties of dipolar exciton condensates in symmetric double layer systems. Recently, the role of screening of additional fermion flavors has been a source of contention in exciton condensates. A room temperature superfluid state has been predicted in bilayer graphene assuming that the condensate screens out additional fermion flavors.\footnote{H. K. Min, R. Bistritzer, J. J. Su and A. H. MacDonald.\emph{Phys. Rev.} B \textbf{78}, 121401 (2008)} On the other hand, large-N calculations have resulted in much weaker screening of fermion flavors and have placed the transition temperature far lower, around one millikelvin.\footnote{M. Y. Kharitonov and K. B. Efetov, \emph{Semicond. Sci. Technol.} \textbf{25}, 034004 (2010)} We demonstrate the effect of added fermion flavor on the Kosterlitz-Thouless transition temperature ($T_{KT}$) in symmetric electron-hole bilayers by collecting static and dynamic response functions.\footnote{J. Shumway and M. J. Gilbert, \emph{arXiv:1108.6107} (2011)} We find that the addition of fermion flavors decreases $T_{KT}$, however, due to strong exciton binding, the decrease we observe is not as drastic as is predicted in the earlier large-N calculations.