| Motivated by the multiband scenario for the iron-based superconductors, we discuss frustration effects in a clean multiband superconductor induced by repulsive interband interactions. We show that these frustration effects lead to one or several phase transitions with increasing temperature from or to chiral superconducting states with broken time-reversal symmetry with continuous evolution of the relative phases of the superconducting order parameters. These transitions are signalled by slope changes in the temperature dependence of the superconducting gaps. In the case of quasi-2D superconductors, such transitions also occur with increasing in-plane magnetic field. |
|