Ch 32.2 A geometric phase $\gamma_n = i\oint\langle n(\mathbf{R})|\nabla_\mathbf{R}|n(\mathbf{R})\rangle\cdot d\mathbf{R}$ acquired by a quantum state when parameters of the Hamiltonian are varied adiabatically around a closed loop. Unlike dynamical phase, Berry phase depends only on the geometry of