@article{chen_li_liang_2006, 
  title={Critical property of the geometric phase in the Dicke model}, 
  volume={74}, 
  DOI={10.1103/physreva.74.054101}, 
  publisher={American Physical Society (APS)}, 
  author={Chen and Li and Liang}, 
  year={2006}, 
  month={Nov}
  }