Novel dielectric anomaly in the hole-doped La2Cu1-xLixO4 and La2-xSrxNiO4 insulators: Signature of an electronic glassy state

The low-frequency dielectric response of hole-doped insulators La2Cu1-xLixO4 and La2-xSrxNiO4 shows a large dielectric constant epsilon(') at high temperature and a steplike 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.