A Novel Dielectric Anomaly in Cuprates and Nickelates: Signature of an   Electronic Glassy State
  The low-frequency dielectric response of hole-doped insulators La_{2}Cu_{1-x}Li_{x}O_{4} and La_{2-x}Sr_{x}NiO_{4} shows a large dielectric constant \epsilon ^{'} at high temperature and a step-like drop by a factor of 100 at a material-dependent low temperature T_{f}. T_{f} increases with frequency and the dielectric response shows universal scaling in a Cole-Cole plot, suggesting that a charge glass state is realized both in the cuprates and in the nickelates. 
Tuson Park, Z. Nussinov, K. R. A. Hazzard, V. A. Sidorov, A. V.   Balatsky, J. L. Sarrao, S.-W. Cheong, M. F. Hundley, Jang-...