Explanation

There is a certain energy gap between the lowest excited state and the ground state of superconductors. According to BCS theory, splitting a Cooper electron pair or exciting two electrons to half of the minimum energy of normal state is called energy gap. The existence of energy gap is one of the bases of superconductivity microscopic theory. The BCS theory derives the existence of energy gap from the basic principles of quantum mechanics, and predicts that its relationship with temperature, d (0) and critical temperature is energy gap at absolute zero. The discovery of energy gap laid the foundation for the establishment of BCS theory. However, the energy gap is not a necessary condition for the existence of superconductivity. Some impurities can reduce the critical temperature of superconductors, but it makes the energy gap decrease faster. Above a certain impurity concentration, the energy gap has been reduced to zero, but it is still a limited value. This leads to the emergence of superconductors with magnetic fields that can cause gaps.

Classification