Berry mechanism

The Berry mechanism, also known as the Berry phase or Berry's phase, is a fundamental concept in quantum mechanics and condensed matter physics. It describes a geometric phase acquired by the quantum state of a system when the system is subject to adiabatic (slow) changes in its parameters. The core idea is that when a quantum system is driven around a closed loop in parameter space, its wave function can acquire a phase factor that is not attributed to the dynamics of the system itself (i.e.