Final answer:
To determine if a material is in the superconducting phase, look for the presence of an energy gap. Gapless edge states are characteristic of topological superconductors.
Step-by-step explanation:
In order to determine whether a material is in the superconducting phase, we can look for the presence of an energy gap. When a material becomes superconducting, a relatively large energy gap forms around the Fermi energy. If this state is destroyed, the gap disappears and the material loses its superconducting properties.
As for the presence of gapless edge states, this is a characteristic of certain types of superconductors called topological superconductors. These superconductors have special properties that give rise to novel phenomena, such as the existence of gapless edge states.