Transient negative capacitance in ferroelectric and twist-bend ferroelectric nematic liquid crystals

Abstract

The negative capacitance (NC) of ferroelectric materials can be used in conventional electronics to reduce power dissipation. Recently, NC was shown (N. P. Dhakal, A. Adaka, R. J. Twieg, N. A. Clark and A. Jákli, Phys. Rev. Appl., 2025, 24, 014029, DOI: 10.1103/fjx3-jd2y) to exist in a fluid ferroelectric nematic (N_F) liquid crystal material as well. Studies presented in this paper strongly indicate that NC exists in all ferroelectric nematic liquid crystal materials provided that the polarization switching time is larger than the rise time of the applied square-wave voltage. Additionally, NC was studied in a recently discovered fluid twist-bend ferroelectric nematic liquid crystal (N_TBF) material while switching its ferroelectric polarization. In contrast to the 2 NC ranges found in conventional ferroelectric crystals and ferroelectric nematic liquid crystals, in the N_TBF phase, the polarization switching happens in two steps leading to four negative capacitance ranges in the P–V hysteresis curves. Our measurements and analyses also provide estimates of the rotational viscosities and the physical mechanisms of the polarization switching steps in the N_TBF phase.