  A wide variety of two-dimensional electron systems (2DES) allow for
independent control of the total and relative charge density of two-component
fractional quantum Hall (FQH) states. In particular, a recent experiment on
bilayer graphene (BLG) observed a continuous transition between a compressible
and incompressible phase at total filling $\nu_T = \frac{1}{2}$ as charge is
transferred between the layers, with the remarkable property that the
incompressible phase has a finite interlayer polarizability. We argue that this
occurs because the topological order of $\nu_T = \frac{1}{2}$ systems supports
a novel type of interlayer exciton that carries Fermi statistics. If the
fermionic excitons are lower in energy than the conventional bosonic excitons
(i.e., electron-hole pairs), they can form an emergent neutral Fermi surface,
providing a possible explanation of an incompressible yet polarizable state at
$\nu_T = \frac{1}{2}$. We perform exact diagonalization studies which
demonstrate that fermionic excitons are indeed lower in energy than bosonic
excitons. This suggests that a "topological exciton metal" hidden inside a FQH
insulator may have been realized experimentally in BLG. We discuss several
detection schemes by which the topological exciton metal can be experimentally
probed.
