  External-field driven energy-level discretization, such as Landau
quantization or Stark localization, is one of the most intriguing phenomena in
quantum systems. We investigate the emergence of the Wannier-Stark ladder
coming from the particle-hole continuum and the Stark shifts of the exciton
levels in one-dimensional Mott insulators under the dc electric field. The
discretized peak structure in the optical-conductivity spectra newly appears by
applying the dc electric field, and the positions of these peaks can be
reproduced from the energy levels of a simple effective model in the
strong-coupling regime. Our results not only suggest that Mott insulators can
serve as a viable platform for Stark discretization, but also pave the way for
investigations of dynamical properties in correlated many-body systems under a
dc electric field.
