  We construct a gravity dual for charge density waves (CDW) in which the
translational symmetry along one spatial direction is spontaneously broken. Our
linear perturbation calculation on the gravity side produces the frequency
dependence of the optical conductivity, which exhibits the two familiar
features of charge density waves, namely the pinned collective mode and gapped
single-particle excitation. These two features indicate that our gravity dual
also provides a new mechanism to implement the metal to insulator phase
transition by CDW, which is further supported by the fact that d.c.
conductivity decreases with the decreased temperature below the critical
temperature.
