Comment on “Photoluminescence Ring Formation in Coupled Quantum Wells: Excitonic Versus Ambipolar Diffusion”

A Comment on the Letter by M. Stern et al., Phys. Rev. Lett. 101, 257402 (2008). The authors of the Letter offer a Reply.

Figure 1

The factor $f=E_{\mathrm{int}}/(n{u}_0)$ against the density $n$ of indirect excitons. Inset (a): The classical dipole-dipole potential $U=U_{dd}(r)$ and a more realistic $U=U_{xx}(r)$, along with form factors $g=g_{dd}(r)$, $g_{xx}(r)$, and $g_{\mathrm{Stern}}(r)$. Inset (b): $n(T)$ and $n_{e,h}(T)$ for $n+n_{e,h}={10}^{10}{\mathrm{cm}}^{-2}$ and $2\times {10}^{10}{\mathrm{cm}}^{-2}$, evaluated with the quantum mass action law. To mimic the experiment [1], $d=13.5\mathrm{nm}$, $M_x=0.215m_0$, and $\epsilon =12.5$ are used.