  Holographic strange metals are known to have a power law resistivity rising
with temperature, which is reminiscent of the strange metal phases in condensed
matter systems. In some holographic models, however, the exponent of the power
law in the resistivity can be negative. In this case one encounters phases with
diverging resistivity at zero temperature: holographic strange insulators.
  These states arise as a result of translational symmetry breaking in the
system, which can either be strong explicit and relevant in the IR, or
spontaneous, but pinned by a small explicit source. In some regards, one can
associate these two classes to the normal band insulators due to the strong
ionic potential, and Mott insulator due to the commensurate lock in of the
charge density wave.
  We study different features of these classes on the explicit example of a
holographic helical model with homogeneous Bianchy VII type translational
symmetry breaking, and uncover the main mechanisms underlying transport in
these two cases. We find that while transport in the explicit relevant case is
governed by the incoherent conductivity, in the pinned spontaneous case the
leading contribution comes from the coherent part.
