  I make a novel contact between string theory and degenerate fermion dynamics
in thin semiconductors. Utilizing AdS/CFT correspondence in string theory and
tunability of coupling parameters in condensed matter systems, I focus on the
possibilities testing string theory from tabletop experiments. I first discuss
the observation that stability of Fermi surface is classifiable according to
K-theory. I then elaborate two concrete realization of Fermi surfaces of zero
and two dimensions. Both are realized by complex of D3-branes and D7-branes of
relative codimension 6 and 4, respectively. The setup with Fermi point models
gauge dynamics of multiply stacked graphenes at half-filling. I show that
string theory predicts dynamical generation of mass gap and metal-insulator
quantum phase transition at zero temperature. I emphasize that conformally
invariant gauge theory dynamics of the setup plays a crucial role, leading to
novel conformal phase transition. The setup with Fermi surface is in
collaboration with Dongsu Bak and is based on charged black hole and models
relativistic Fermi liquid. We find positive evidence for this identification
from both equilibrium thermodynamics at or near zero temperature and
out-of-equilibrium linear response and transport properties. I argue that
fluctuation of black hole horizon provides holographic realization consistent
with Fermi liquid for thermodynamics and interesting departures therefrom in
transport properties.
