  We study the stability of topologically protected zero-energy flat bands at
the surface of nodal noncentrosymmetric superconductors, accounting for the
alteration of the gap near the surface. Within a selfconsistent mean-field
theory, we show that the flat bands survive in a broad temperature range below
the bulk transition temperature. There is a second transition at a lower
temperature, however, below which the system spontaneously breaks time-reversal
symmetry. The surface bands are shifted away from zero energy and become weakly
dispersive. Simultaneously, a spin polarization and an equilibrium charge
current develop in the surface region.

Superconductivity