Competition between quantum fluctuations and antiferroelectric order in Ru-doped Sr0.8Ca0.2Ti1-xRuxO3

The competition between quantum fluctuations and the antiferroelectric state in Sr0.8Ca0.2Ti1-xRuxO3 is investigated by measuring the low-temperature dielectric permittivity and by Raman spectroscopy. We demonstrate the significant impact of quantum fluctuations on the stability of the antiferroelectric polar order. It is revealed that the structural phase transitions can be modified by the quantum fluctuations, enhancing the stability of the high-symmetry phase and suppressing the antiferroelectric transitions. More importantly, a quantum antiferroelectric state, exhibiting similar behavior as the quantum ferroelectric state in terms of dielectric response, is identified. In addition, the effect of quantum fluctuations on the increasing permittivity at low temperature is also discussed.