Dielectric Properties of a Ferroelectric Nematic Material: Quantitative Test of the Polarization-Capacitance Goldstone Mode

The recently discovered ferroelectric nematic (N₅) liquid crystals (LC) have been reported to show an extraordinarily large value of the real part of the dielectric constant (ϵ^'>10^3) at low frequencies. However, it was argued by Clark et al. in Phys. Rev. Res. 6, 013195 (2024) that what was measured was the capacitance of the insulating layer at LC or electrode surface and not that of the liquid crystal. Here we describe the results of dielectric spectroscopy measurements of an N₅ material in cells with variable thickness of the insulating layers. Our measurements quantitatively verify the model by Clark et al. Additionally, our measurements in cells with bare conducting indium tin oxide surface provide a crude estimate of ϵ_10^2 in the N₅ phase.