We study the dependence of the superconducting gaps on both the disorder and the\ntemperature within the two-band model for iron-based materials. In the clean limit, the system is in\nthe sâ?¦ state with sign-changing gaps. Scattering by nonmagnetic impurities leads to the change of the\nsign of the smaller gap, resulting in a transition from the sâ?¦ to the sâ?¦ state with the sign-preserving\ngaps. We show here that the transition is temperature-dependent. Thus, there is a line of sâ?¦\ntransition in the temperatureâ??disorder phase diagram. There is a narrow range of impurity scattering\nrates, where the disorder-induced sâ?¦ transition occurs at low temperatures, but then the\nlow-temperature sâ?¦ state transforms back to the sâ?¦state at higher temperatures. With increasing\nimpurity scattering rate, the temperature of such â?¦ sâ?¦ transition shifts to the critical temperature\ntc, and only the sâ?¦ state is left for higher amounts of disorder.
Loading....