"Tri-refringence, Superprisms, and Pulses-on-the-fly in Photonic Crystal Waveguides"
Prof. Jeremy J. Baumberg

Oct 28, 2003

講演題目：　Tri-refringence, Superprisms, and Pulses-on-the-fly in Photonic Crystal Waveguides
講　師　：　Prof. Jeremy J. Baumberg
　　　　　(Department of Physics & Astronomy, University of Southampton, and Mesophotonics Ltd., Chilworth Science Park,Southampton, S016 7NP, UK)
日　時　：　平成15年10月28日 (火) 17:00-
場　所　：　北海道大学大学院工学研究科 量子物理工学専攻会議室 A3-62

要　旨　：
Photonic Crystal Waveguides promise novel optical functionality in a wide variety of ways due to the considerable modification in optical propagation and interactions induced in these sub-micron periodic structures. Using planar silicon-compatible processing we have produced a wide variety of nanostructured devices over the past few years [1-8] that exhibit high quality photonic bandgap and photonic crystal features. In particular we have gained an understanding of such devices of ultrawide bandwidth ranges allowing us to provide systematic comparison with a variety of our modelling techniques. Recently we have explored how light propagates through photonic crystals by directly tracking the temporal delay of each wavepacket component [1]. In this talk we will discuss a number of the features of photonic crystal waveguides that we are investigating.
[1] "Separation of Photonic Crystal Waveguides Modes using Femtosecond Time-of-Flight", M. C. Netti, C. Finlayson, J. J. Baumberg et al. Appl. Phys. Lett. 81, 3927 (2002).
[2] "Optical Trirefringence in Photonic Crystal Waveguides", M.C. Netti, A. Harris, J.J. Baumberg et al., Phys. Rev. Lett. 86, 1526 (2001).
[3] "Complete and absolute photonic bandgaps in highly symmetric photonic quasicrystals embedded in low refractive index materials", M.E. Zoorob et al., Mat.Sci.Eng.B 74, 168 (2000).
[4] "Experimental investigation of photonic crystal waveguide devices and line-defect waveguide bends", M.D.B. Charlton et al., Mat.Sci.Eng.B 74, 17 (2000).
[5] "Complete photonic bandgaps in 12-fold symmetric quasicrystals", M.E. Zoorob, M.B.D. Charlton, G.J. Parker, J.J. Baumberg and M.C. Netti, Nature 404, 740 (2000).
[6] "Visible Photonic Bandgap Engineering in Silicon Nitride Waveguides", M.C. Netti, M.B.D. Charlton, G.J. Parker, J.J. Baumberg, Appl. Phys. Lett. 76, 991 (2000).
[7] "Guided mode analysis, and fabrication of a 2-dimensional visible photonic band structure confined within a planar semiconductor waveguide", M.D.B. Charlton et al., Mat.Sci.Eng.B 49, 155 (1997).
[8] "Ultra-Broadband Transmission Measurements on Waveguides of Silicon-Rich Silicon Dioxide", RT Neal, CE Finlayson, MC Netti, MDCCharlton, GJ Parker, JJ Baumberg, Appl. Phys. Lett. (2003).

世話人　 松田 理
（omatsuda@eng.hokudai.ac.jp)
北海道大学大学院工学研究科

"LC PHASES FORMED BY BANANA-SHAPED MOLECULES POSSIBLE CONSEQUENCES OF TETRAHEDRATIC ORDER"
Prof. Helmut R. Brand

Oct 14, 2003

講演題目：　LC PHASES FORMED BY BANANA-SHAPED MOLECULES POSSIBLE CONSEQUENCES OF TETRAHEDRATIC ORDER
講　師　：　Prof. Helmut R. Brand
　　　　　(Theoretische Physik III, Universitat Bayreuth, 95440 Bayreuth, Germany)
日　時　：　平成15年10月14日 (火) 11:00-
場　所　：　北海道大学大学院理学研究科物理学専攻　大学院講義室 理学部　2号館（2－11号室）

要　旨　：
　　Some of the most interesting developments in liquid crystals over the last few years are related to the physical properties of the liquid crystalline phases exhibited by banana-shaped (bent-core) molecules.
　　Experimental evidence to date suggests that this is indeed a new sub-field of thermotropic liquid crystals. The biggest challenge is the condensed state known as B7 that grows into the isotropic liquid with many different growth patterns including spirals with both hands. Neither the symmetry nor the physical properties of B7 are understood. A tetrahedratic phase, T, is described by four unit vectors, n1 to n4, oriented along the four tetrahedral corners of a cube. It has the symmetry:
T (- n^a) = - T ( n^a) (a = 1,2,3,4);
that is odd under parity. As tetrahedra are not space-filling objects, they can be viewed equally well as precursors of condensed lamellar and/or columnar mesophases. Tetrahedratics are thus a model for studying frustrated lamellar and columnar liquid crystalline phases with many different condensed states that are energetically very close together. In a first step we analyzed the coupling of flow to electric fields and temperature gradients assuming that the symmetry of the tetrahedratic phase is unchanged by the external forces. We also discuss what happens when the tetrahedral angle is allowed to change under the influence of external forces and fields. We also analyze how an external electric field applied to an isotropic tetrahedratic phase can induce orientational order Qij as well as smectic layering. The relation of our analysis to recent experimental observations by Weissflog et al. will be discussed. Work done in collaboration withP.E. Cladis and Harald Pleiner

世話人　 北　孝文
（kita@phys.sci.hokudai.ac.jp)
北海道大学大学院理学研究科

「有機超伝導体の量子渦糸状態」
佐々木 孝彦 氏

Oct 02, 2003

講演題目：　有機超伝導体の量子渦糸状態
講　師　：　佐々木 孝彦 氏
　　　　　(東北大学・金属材料研究所・助教授)
日　時　：　平成15年10月2日 (火) 16:30-
場　所　：　北海道大学大学院理学研究科物理学専攻　大学院講義室 理学部　2号館 4階 9号室 (2-4-09)

要　旨　：
　　酸化物高温超伝導体における渦糸状態の研究により第２種超伝導体の渦糸に関する理解が飛躍的に進歩した．その中でも新しい渦糸相とその相転移が明らかにされてきた．このような渦糸物理は，高温超伝導体にのみ固有ではなくゆらぎの大きい２次元系であれば他の物質系でも統一的に理解，観測されるはずである．さらに新たな物質パラメーターを有する系では新奇な渦糸物理の展開が期待される．有機超伝導体は超伝導転移温度は約１０Kと低いが，大きな２次元異方性，低キャリア密度などゆらぎ効果が顕著な系である．また極めてクリーンな電子系を有し，磁気量子振動効果による詳細な電子状態研究が可能な系でもある．このような特徴を有する有機超伝導体の渦糸状態に関する現状をレビューし，最近，我々が見出した「新渦糸状態-量子磁束スラッシュ-」と「渦糸状態での磁気量子振動効果」について紹介する．

世話人　 松永 悟明
（mat@phys.sci.hokudai.ac.jp)
北海道大学大学院理学研究科

「高輝度放射光による物質科学の最近の進展」
壽榮松 宏仁 氏

Sep 25, 2003

講演題目：　高輝度放射光による物質科学の最近の進展
講　師　：　壽榮松 宏仁 氏
　　　　　(SPring-8 / JASRI 　利用研究促進部門I　部門長)
日　時　：　平成15年9月25日 (火) 16:30-
場　所　：　北海道大学大学院理学研究科物理学専攻　大学院講義室 理学部　2号館（2－11号室）

要　旨　：
　　第３世代の放射光施設の出現によって、放射光X線による物質科学は種々の分野で著しく発展した。これは、アンデュレーターによる放射光の持つ特性、高強度、高輝度、高並行性および高エネルギー分解能が、従来のX線回折・散乱・分光による測定手法を大きく変身させたことにある。たとえば、電子密度分布決定などの精密構造解析、磁気構造や電子軌道の決定、高分解能非弾性散乱によるフォノン分散関係の測定、X線マイクロビームによる微量元素マッピングなどの顕微計測法の開発など、第３世代光源によって始めて可能となった測定手法による物質科学が急速に発展している。
　　本講演では、これらSPring-8を中心とする高輝度放射光源による最近の進展を紹介する。

世話人　 中原　純一郎
（jun@phys.sci.hokudai.ac.jp)
北海道大学大学院理学研究科

"Realization of the FFLO state in CeCoIn₅ at ambient pressure: a simple lesson about extreme conditions’ research"
Dr. Stan Tozer

Jul 28, 2003

講演題目：　Realization of the FFLO state in CeCoIn₅ at ambient pressure: a simple lesson about extreme conditions’ research
講　師　：　Dr. Stan Tozer
　　　　　(The National High Magnetic Field Laboratory Tallahassee, Florida, U.S.A.)
日　時　：　平成15年7月28日 (火) 14:00-15:00
場　所　：　北海道大学大学院理学研究科物理学専攻　大学院講義室 理学部　2号館（2－11号室）

要　旨　：
　 　A brief introduction to recent high pressure transport and magnetization experiments in pulsed and dc magnetic fields and some promising initial results will be followed by a presentation of our ambient pressure studies of the FFLO state recently found in CeCoIn₅. This phase was first predicted in 1964 by Fulde & Ferrell and, independently, Larkin & Ovchinnikov. They showed that, in the paramagnetic limit, an applied magnetic field H coupling to the individual electron spins of superconducting Cooper pairs could induce a phase transition from a uniform to a novel, spatially varying superconducting phase. Buzdin and Brison predicted in 1996 that, within this FFLO phase, solutions corresponding to higher Landau level states of the order parameter should occur. I will present heat capacity measurements on the layered structure heavy fermion superconductor CeCoIn₅ revealing a phase transition within the standard BCS superconducting state at high field and low temperature for fields parallel to the layers. Within this wedge of phase space, our magnetization measurements display a cascade of first order phase transitions. The observation of steps in the magnetization is a result of orbital quantization of the order parameter and, with the heat capacity measurements, provides the first direct evidence of the existence of the FFLO phase. The work presented is the result of an extensive collaboration funded by an NHMFL In-house research proposal, the State of Florida, the Department of Energy, and the National Science Foundation. I would like to acknowledge my colleagues H.A. Radovan, T.P. Murphy, S.T. Hannahs, E.C. Palm, N.A. Fortune, C. Agosta, I. Mihut, C. Catalin, D. Hall, J. Singleton, and A. Bangura.

世話人　 網塚　浩
（amiami@phys.sci.hokudai.ac.jp)
北海道大学大学院理学研究科