  We present a new impurity solver for dynamical mean-field theory based on
imaginary-time evolution of matrix product states. This converges the
self-consistency loop on the imaginary-frequency axis and obtains
real-frequency information in a final real-time evolution. Relative to
computations on the real-frequency axis, required bath sizes are much smaller
and less entanglement is generated, so much larger systems can be studied. The
power of the method is demonstrated by solutions of a three band model in the
single and two-site dynamical mean-field approximation. Technical issues are
discussed, including details of the method, efficiency as compared to other
matrix product state based impurity solvers, bath construction and its relation
to real-frequency computations and the analytic continuation problem of quantum
Monte Carlo, the choice of basis in dynamical cluster approximation, and
perspectives for off-diagonal hybridization functions.
