Transient Negative Capacitance in Ferroelectric Nematic Liquid Crystals

Abstract: The transient negative capacitance (NC) of solid ferroelectric materials used in field effect transistors can reduce the power dissipation of electronics. Here we show that similar negative capacitance appears in the recently discovered fluid ferroelectric nematic liquid crystal (FNLC) films while switching their ferroelectric polarization. Instead of sidewise motion of domains with opposite direction of polarization of ferroelectric crystals, in FNLCs the polarization vector that at zero field aligns parallel to the substrates, rotates toward the applied electric field. In spite of that difference, the observed switching time per unit electric field values are comparable. Although current FNLCs have much larger electric conductivity than of ferroelectric crystals, they have several advantages: they are organic, lightweight, can be prepared and operated at ambient temperature, the direction of the polarization can be set by simple surface alignment, and they require much less electric field for switching of the polarization. These properties make FNLCs attractive to test them in in flexible organic electrochemical transistor (OECT) devices.