Yoshiichi Suzuki

Tristable Switching in Surface Stabilized Ferroelectric Liquid Crystals with a Large Spontaneous Polarization

A new switching process was observed in surface stabilized ferroelectric liquid crystals. The switching is associated with a third stable state in addition to the well-known bistable states. The appearance of the third state is characteristic of materials with a large spontaneous polarization and is caused by minimizing induced polarization charges. The switching between each bistable state and the third state exhibits a sharp dc-threshold and hysteresis, suggesting a possible application for a switching device.

Direct measurement of vertical binding energy of a hydrated electron

We present the first measurement of the vertical binding energy (VBE) of a hydrated electron in bulk water by the time-resolved photoelectron spectroscopy (TRPES) of the charge-transfer-to-solvent (CTTS) reaction in aqueous NaI solution. Our best estimate of VBE is 3.27 +/- 0.10 eV for H(2)O and 3.20 +/- 0.10 eV for D(2)O.

New fluorine-containing ferroelectric liquid crystal compounds showing tristable switching

Abstract To understand the real cause of stabilization of the third state and to assure the possible application of the tristable switching, we have studied the effect of chiral centers on the appearance of the third state, synthesizing (R)-(+)- and (S)-(–)-4-(1-trifluoromethylalkoxy(n)carbonyl) phenyl 4′-alkoxy(m)biphenyl-4-carboxylate where m = 8, 9, 10, or 12 and n = 6 or 8; note that the chiral centre has a trifluoromethyl group. By observing light transmittance and switching current responses to a triangular voltage wave and by taking stroboscopic micrographs, we have confirmed that all the materials synthesized show the tristable switching in wide temperature ranges; in particular, the materials with m = 10 or 12 and n = 6 have the stabilized third state even at temperatures below 30°C.

Probing Ultrafast Internal Conversion through Conical Intersection via Time-Energy Map of Photoelectron Angular Anisotropy

The ultrafast S(2) --> S(1) internal conversion of pyrazine through a conical intersection of the potential energy surfaces was clearly observed by ultrafast photoelectron imaging. The 2D time-energy map of the photoelectron angular anisotropy revealed a clear signature of the internal conversion (the color change of green-orange-green in the horizontal direction) at approximately 0.9 eV. The orange color at approximately 20 fs and 0.9 eV was found to correspond to the non-Koopmans ionization process from S(2)(pi,pi*) to D(0)(n(-1)).

Time-resolved photoelectron imaging of ultrafast S2-->S1 internal conversion through conical intersection in pyrazine.

A nonadiabatic electronic transition through a conical intersection was studied by pump-probe photoelectron imaging spectroscopy with a 22 fs time resolution in the benchmark polyatomic molecule of pyrazine and deuterated pyrazine. The lifetimes of the S(2) state of pyrazine and deuterated pyrazine were determined to be 22+/-3 fs by the global fitting of the time-energy maps of photoelectron kinetic energy (PKE) distributions. The lifetime of S(3) was determined to be 40-43 fs. Two-dimensional maps of photoelectron distributions were obtained for time (t) and PKE, and individual PKE distributions upon ionization from S(2) and S(1) were extracted. Quantum beat with an approximately 50 fs period was observed after the S(2)-->S(1) internal conversion, which was attributed to the totally symmetric vibration nu(6a) in S(1).

Ferroelectric Liquid Crystal Display Using Tristable Switching

Smectic layer structure and switching behavior in antiferroelectric liquid crystals TFMHPOBC, TFMHPDBC and MHPOBC were studied. At the phase transition point between SmC* and SmCA*, discontinuity in the leaning angle and the layer spacing was observed. In the SmA phase, diffraction peaks attributable to the focal conic texture and the planar layer structure were observed, implying that the bookshelf structure and the focal conic texture coexist. Using the tristable switching, we designed the fundamental waveforms for multiplex driving and constructed a prototype antiferroelectric liquid crystal display which works at room temperature.

Competition between Ferroelectric and Antiferroelectric Interactions Stabilizing Varieties of Phases in Binary Mixtures of Smectic Liquid Crystals

An electric field-temperature (E-T) phase diagram has been drawn for several binary mixtures of antiferroelectric liquid crystals using conoscopic observation. All the possible phases are SmA-SmCα*-SmC*-new antiferroelectric phase-new ferrielectric phase-SmCγ*-new ferrielectric phase-SmCA*, some of which appear in the above regular order. Two Devils staircases are necessary to elucidate systematic understanding of successive phase transitions among ferroelectric, ferrielectric and antiferroelectric phases: one is a staircase of SmCα*(qT) already discussed by Takanishi et al. and the other is a staircase of SmCA*(qT). Competition between an antiferroelectric interaction responsible for SmCA* and a ferroelectric one for SmC* is considered to stabilize a variety of phases, SmCA*(qT).

Conoscopic study of the Scα∗ phase and the Devil's staircase in an antiferroelectric liquid crystal

Abstract The molecular orientational structure of the Scα∗ phase has been studied by means of X-ray, dielectric and conoscopic measurements for 4-(1-methylheptyloxycarbonyl)phenyl 4′-octylcarbonyloxybiphenyl-4-carboxylate. It was found by X-ray scattering that the Scα∗ phase is tilted. According to the conoscopic observation under a low field, the optic plane of Scα∗ is parallel to the field direction similar to that of the Scα∗ phase of 4-(1-methylheptyloxycarbonyl)phenyl 4′-octyloxybiphenyl-4-carboxylate. It was also found that the molecular orientation of the Scα∗ phase is antiferroelectric in the high temperature region, while in the low temperature region it is ferrielectric and changes with temperature, suggesting the so-called Devils staircase. The critical temperature, where the biaxiality and the tilt angle of the average optic axis have maximum values, was assigned to the ferrielectric state with the largest spontaneous polarization.

On the appearance of antiferroelectricity: The effect of polarization and conjugation in antiferroelectric liquid crystals

Abstract In order to clarify the role of polarization and the conjugation in antiferroelectric liquid crystal molecules (AFLC), systematic series of AFLC compounds containing fluoro-substituent have been synthesized. The polarization of peripheral region of the chiral center and the conjugation along the long axis of an AFLC molecule are responsible for the appearance of the antiferroelectricity. Based on these experimental findings, the conjugated system expected for AFLC molecules is tentatively proposed.

Experimental Studies on Phase Transitions in an Antiferroelectric Liquid Crystal

The effect of optical purity on the antiferroelectric phase transition and the field-induced ferroelectric phase transition in Sm C A * were studied by means of dielectric measurements and observations of D-E hysteresis loops. The Curie-Weiss law was found to hold in Sm A and the Curie-Weiss constant to increase as the optical purity is reduced. Three types of D-E curves were obtained in the Sm C A * phase. It was found that a double hysteresis loop changed into a single one at high frequencies. The results obtained are discussed on the basis of a phenomenological theory