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Band structure reconstruction across nematic order in high quality FeSe single crystal as revealed by optical spectroscopy study

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Science Bulletin 2016年第14期61卷 1126-1131页

作者： Haipeng Wang Zirong Ye Yan Zhang Nanlin Wang Beijing National Laboratory for Condensed Matter Physics Institute of Physics Chinese Academy of SciencesBeijing 100190 China International Center for Quantum Materials School of PhysicsPeking University Beijing 100871 China Collaborative Innovation Center of Quantum Matter Beijing 100871 China

We perform an in-plane optical spectroscopy measurement on high quality FeSe single crystals grown by a vapor transport technique. Below the structural transition at Ts - 90 K, the reflectivity spectrum clearly shows a gradual suppression around 400 cm-1 and the conductivity spectrum shows a peak at higher frequency. The energy scale of this gap-like feature is comparable to the width of the band splitting observed by ARPES. The low-frequency conductivity consists of two Drude components and the overall plasma frequency is smaller than that of the FeAs based compounds, suggesting a lower cartier density or stronger correlation effect. The plasma frequency becomes even smaller below Ts which agrees with the very small Fermi energy estimated by other experiments. Similar to iron pnictides, a clear temperature-induced spectral weight transfer is observed for FeSe, being indicative of strong correlation effect.

关键词： Iron-based superconductor Opticalspectroscopy nematic phase Band reconstruction

nematic and smectic stripe phases and stripe-Sk X transformations

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Science China(Physics,Mechanics & Astronomy) 2022年第4期65卷 112-119页

作者： Hai-Tao Wu Xu-Chong Hu X.R.Wang Department of Physics The Hong Kong University of Science and TechnologyHong Kong 999077China HKUST Shenzhen Research Institute Shenzhen 518057China

Based on the findings of skyrmion nature of stripes and the metastability of a state of an arbitrary number of skyrmions,precisely controlled manipulation of stripes of skyrmion number 1 in pre-designed structures and mutual transformation between helical states and skyrmion crystals(Sk Xs)are demonstrated in chiral magnetic *** a proof of the concept,we show how to use patterned magnetic fields and spin-transfer torques(STTs)to generate nematic and smectic stripe phases,as well as“UST”mosaic from three curved *** one stripe into many pieces and coalescing several skyrmions into one by various external fields are good ways to transform helical states and Sk Xs from each other.

关键词： spintronic Landau-Lifshitz-Gilbert equation simulation stripe skyrmion skyrmion crystal nematic phase

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Cure reaction and phase behavior of liquid crystalline epoxides-anhydride systems

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Chinese Chemical Letters 2007年第2期18卷 225-228页

作者： Li Yan Liang Shao Ping Ren Yi Quan Zheng Man Geng Lu Guangzhou Institute of Chemistry Chinese Academy of SciencesGuangzhou 510650China Key Laboratory of Polymer Materials for Electronics Guangdong 510650China Graduate School of the Chinese Academy of Sciences Beijing 100049China

A series of novel liquid crystalline epoxides with lateral substituents were cured with anhydrides and the cure kinetics was investigated by non-isothermal DSC technique. The results showed that the lengths of lateral substituents have great effect on the value of Ea. The curing reaction became less active, when the liquid crystalline epoxides have long lateral substituents and were controlled by diffusion at the late stage of cure. A nematic structure was observed by POM and XRD.

关键词： Liquid crystalline epoxy resin Anhydride nematic phase Lateral substituent

Liquid Crystalline Behaviours of the Complexes Based on 1,3,4-Oxadiazole Derivative and Benzoic Acid

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Chinese Journal of Chemistry 2012年第4期30卷 785-790页

作者：赵呈孝王海涛冉霞白炳莲张艳李敏 Key Laboratory for Automobile Materials Ministry of EducationInstitute of Materials Science and EngineeringJilin UniversityChangchunJilin 130012China

A non-liquid crystal compound （4-POXD-6） containing the 1,3,4-oxadiazole group and pyridyl （py） group was synthesized. And a series of supramolecular mesogenic complexes were obtained by mixing 4-POXD-6 and 4-alkoxybenzoic acids （Cn, n=6, 8, 12）. The liquid crystalline properties of4-POXD-6/Cn （n=6, 8, 12） were in- vestigated by means of differential scanning calorimetry, polarized optical microscopy, and wide-angle X-ray dif- fraction. It was found that 4-POXD-6/Cn （6, 8） display monotropic nematic and smectic A phases, while 4-POXD-6/C12 exhibits a SmX phase in the heating process and a SmA phase in the cooling run. Vari- able-temperature FTIR spectroscopic studies revealed hydrogen bonds existed in both crystalline and liquid crystal- line phases.

关键词： 1,3,4-oxadiazole nematic phase smectic A hydrogen bonding pyridyl

Studies on Liquid Crystalline Bis[4-(p-phenoxy)-phenylbenzoate]Alkyldicarboxylat

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Chemical Research in Chinese Universities 1998年第2期14卷 91-95页

作者： XING Pei-xiang TIAN Yan-qing WANG Jun-zuo NA Hui TANG Xin-yi JIANG Bing-zheng Polymer Physics Laboratory Changchun Institute of Applied ChemistryChangchun130022 Department of Chemistry Jilin Univer sityChangchun130023

A new series of liquid crystals of bis[4-(p-phenoxy)-phenylbenzoate]-alkyldicarboxylate which contain two rigid groups connected by a flexible spacer was synthesized. These liquid crystals show nematic phase and were ... 详细信息

关键词： Liquid crystal nematic phase Odd-even effect

MORPHOLOGY OF A THERMOTROPIC AROMATIC POLYESTER

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Chinese Journal of Polymer Science 1992年第2期10卷 158-163页

作者：陈寿羲金永泽徐懋 Institute of Chemistry Academia Sinica Beijing 100080

The crystalline morphology of a thermotropic aromatic polyester has been studied by microscopy techniques. Spherulites with ringed structure under polarizing micioscope were observed for solution cast specimens, They were composed of radially growing crystalline lamellae of thickness around 100. It was found that the molecules were packed in the thickness direction. Banded texture was observed in randomly packed domains for melt cast specimens. The bands have the same width and internal structure as those usually observed in oriented specimens of these polymers obtained by shearing their mesomorphic melt.

关键词： Spherulite Schlieren texture Banded texture nematic phase aromatic polyester.

Polarizabilities and Orientational Order Parameter in N-(p-n-Ethoxybenzylidene)- p-n-Alkoxy Anilines, *** LC Compounds

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Journal of Surface Engineered Materials and Advanced Technology 2016年第3期6卷 134-148页

作者： Putcha Srinivasa Sastry Chintalapati Srinivas Pokkunuri Pardhasaradhi Venkata Gopala Krishna Murthy Pisipati Department of Physics Krishna University Machilipatnam India Department of Physics A. L. College Vijayawada India Liquid Crystal Research Centre Department of Electronics and Communications Engineering Koneru Lakshmaiah University Vaddeswaram India

n.m, ***, nO.m and *** compounds play an important role in the fundamental and applied aspects. As a part of our systematic studies of the above homologous series regarding the synthesis, characterization and phase transition studies, here the authors report the polarizabilities and orientational order parameter, S in N-(p-n-ethoxybenzylidene)-p-n-alkoxy anilines, *** with m = 3 to 10 liquid crystalline compounds except with m = 5 which has been already published. The rest of the compounds exhibit the nematic LC phase except with m = 10 which shows the smectic-C phase along the nematic phase which is originally not detected by Godzwon et al. But the author’s observations with TM and differential scanning calorimeter have shown the existence on SmC phase in addition to nematic phase. Further, SmC is clarified using the histogram technique whose details are given below and are published elsewhere. The orientstonal order parameter, S is estimated using different methods and compared with the value obtained from birefringence, δn = (ne – no) where no field model is used. It is observed in these compounds case as in other LC compounds Vuks isotropic model is favored compared to that of anisotropic model proposed by Neugebauer.

关键词： Orientstonal Order Parameter S 2O.Om LC Compounds Vuks Isotropic Model Neugebauer Anisotropic Model nematic phase

SYNTHESIS AND CHARAOTERIZATION OF NOVEL THERMOTROPIO LIQUID ORYSTALLINE POLYESTERS BEARING NONLINEAR OPTICAL AZOBENZENE SIDE GROUP

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Transactions of Tianjin University 1999年第1期5卷 93-97页

作者：张会旗张莹甘湘萍阴航明孙经武天津大学化工学院南开大学高分子化学研究所吸附分离功能高分子材料国家重点实验室

A series of novel thermotropic liquid crystalline polyesters bearing nonlinear optical azobenzene side group were synthesized by high temperature solution polycondensation and their structures,thermal stability, phase transition behavior and crystallinity were characterized by IR,elemental analysis, TG-DTA, polarizing optical microscope (POM) equipped with a hot stage and X-ray diffraction techniques. The results demonstrate that all the synthesized polyesters exhibit nematic liquid crystalline phases and show relatively high glass transition temperatures and good thermal stability.

关键词： azobenzene polyester thermotropic liquid crystalline polymer nematic phase nonlinear optical material