Fermi edge singularity in photoluminescence of graphene

We investigated the Fermi-energy (${E}_{\mathrm{F}}$) dependence of the photoluminescence (PL) of monolayer graphene. The steady-state PL spectra for $2|{E}_{\mathrm{F}}|=0.80$, 1.04, and 1.22 eV (the origin of electron energy was set at the Dirac point) showed a high-energy shift of the spectral edge (Fermi edge) with an increase in $2|{E}_{\mathrm{F}}|$. The PL decay curve at a PL photon energy (${E}_{\mathrm{PL}}$) of 1.10 eV was observed in the ${E}_{\mathrm{F}}$ range of +0.30 to \ensuremath{-}0.61 eV. It was found that the ${E}_{\mathrm{F}}$ dependence of the maximum intensity in each PL decay curve had the largest value at ${E}_{\mathrm{F}}=\ensuremath{-}0.55\ifmmode\pm\else\textpm\fi{}0.06\phantom{\rule{0.28em}{0ex}}\mathrm{eV}$, and ${E}_{\mathrm{PL}}\ensuremath{\sim}2|{E}_{\mathrm{F}}|$. The observed results are discussed in terms of the Fermi edge singularity due to many-body electron-hole interactions.