  We study the fermionic spectral density in a strongly correlated quantum
system described by a gravity dual. In the presence of periodically modulated
chemical potential, which models the effect of the ionic lattice, we explore
the shapes of the corresponding Fermi surfaces, defined by the location of
peaks in the spectral density at the Fermi level. We find that at strong
lattice potentials sectors of the Fermi surface are unexpectedly destroyed and
the Fermi surface becomes an arc-like disconnected manifold. We explain this
phenomenon in terms of a collision of the Fermi surface pole with zeros of the
fermionic Green's function, which are explicitly computable in the holographic
dual.
