Topological Order: From Long-Range Entangled Quantum Matter to a Unified Origin of Light and Electrons
(a) Disordered states that do not break the symmetry. (b) Ordered states that spontaneously break the symmetry. The energy function has a symmetry . However, as we change the parameter , the minimal energy state (the ground state) may respect the symmetry (a), or may not respect the symmetry (b). This is the essence of spontaneous symmetry breaking.