Wave-packet dynamics in slowly perturbed crystals: Gradient corrections and Berry-phase effects

  title={Wave-packet dynamics in slowly perturbed crystals: Gradient corrections and Berry-phase effects},
  author={Ganesh Sundaram and Q. Niu},
  journal={Physical Review B},
We present a unified theory for wave-packet dynamics of electrons in crystals subject to perturbations varying slowly in space and time. We derive the wave-packet energy up to the first-order gradient correction and obtain all kinds of Berry phase terms for the semiclassical dynamics and the quantization rule. For electromagnetic perturbations, we recover the orbital magnetization energy and the anomalous velocity purely within a single-band picture without invoking interband couplings. For… 
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