Topological Charge Pumping in Excitonic Insulators.

  title={Topological Charge Pumping in Excitonic Insulators.},
  author={Zhiyuan Sun and Andrew J. Millis},
  journal={Physical review letters},
  volume={126 2},
We show that in excitonic insulators with s-wave electron-hole pairing, an applied electric field (either pulsed or static) can induce a p-wave component to the order parameter, and further drive it to rotate in the s+ip plane, realizing a Thouless charge pump. In one dimension, each cycle of rotation pumps exactly two electrons across the sample. Higher dimensional systems can be viewed as a stack of one-dimensional chains in momentum space in which each chain crossing the Fermi surface… 

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