セミナー・特別講義

2011年度

GCOEセミナー
title

Superconductors and ferromagnets in contact: from thin films to nanostructure

author

Professor H. v. Lohneysen

Karlsruhe Institute of Technology (KIT)
date
2012年3月29日(木)10:00
place
理学研究科5号館401号室
abstract
The interest in interfaces of metals with different groundstates has a long history. In recent years, the contact between a superconductor S and a ferromagnet F has received a lot of attention. Cooper pairs can penetrate from S into F, but experience the exchange field of F. The latter causes an oscillation of the pair amplitude leaking from S into F which leads to oscillations of the superconducting critical temperature Tc and of the critical current in S/F/S triple layers as a function of the F-layer thickness. The microscopic process of this “proximity effect”, i.e., the finite pair amplitude outside S - of course also present between S and a normal metal N - is Andreev reflection (AR) described as a coherent process of an electron from N (or F) incident on S and being reflected as a hole, thus generating a Cooper pair in S. In turn, Tc of an F/S/F trilayer depends on the relative magnetization direction of the two F layers. We have investigated this “spin switch effect” using F layers with perpendicular magnetic anisotropy [1,2]. ? Because of the spin structure of the Cooper pair (singlet for conventional superconductors) AR can be used as a tool to investigate the spin-dependent transport through an S/F interface. This however, requires the use of nanostructured contacts. We have investigated S/F contacts of typical diameters of 10-20 nm prepared by e-beam lithography with S = Al and F = Fe, Co, Ni, in order to determine the relation between the spin polarization PAR of the AR-induced current through the contact, and the spin polarization PB obtained for pure F materials by, e.g., spin-resolved photoemission [3]. We find a systematic dependence of PAR on the resistance of the contact which is attributed to spin-orbit scattering [4]. ? The coherent AR process occurs on a length scale of the coherence length ξS in S. Thus, the injection of an electron into S through one electrode and reflection of a hole into a second electrode is possible if both electrodes are placed within ξS. The use of F electrodes provides a means to detect this nonlocal AR, again by virtue of the spin structure of Cooper pairs. The observation [5] of nonlocal (or crossed) AR has opened the avenue to search for entangled, but spatially separated, Einstein-Podolski-Rosen pairs in solids. Nonlocal AR competes with another non-local process, i. e., electron cotunneling, leading to oscillations in the non-local conductance of injector and detector bias [6].
contact
Matsuda
( matsuda@scphys.kyoto-u.ac.jp)
note
GCOEセミナー
title
New Electron Microscope based on Coherent Diffraction Imaging
author
Dr. Tsumoru Shintake 
(沖縄OIST大学 教授)
date
2012年3月2日(金曜日) 15:00−17:00
place
理学研究科5号館525  第4講義室
abstract
Recently phase retrieve has been realized based on iterative fast FFTs in optics and X-ray FELs. We further advance this mathematic technique and apply on coherent electron beam, and develop following microscopes for biology: 
・We study basic interaction of low energy coherent electron and atoms.
・We develop new concept of atomic resolution SEM (scanning electron microscope) using digital holography technique on coherent diffraction.
・We perform electron crystallography on nano-crystals of membrane proteins.
・We also participate SACLA Free Electron Laser experiments.
With these atomic resolution microscopes, we will obtain 3D image of atomic structures in DNA, virus, and proteins, in few years.
contact
中家
( t.nakaya@scphys.kyoto-u.ac.jp)
note
GCOEセミナー
title
New Electron Microscope based on Coherent Diffraction Imaging
author
Dr. Tsumoru Shintake 
(沖縄OIST大学 教授)
date
2012年3月2日(金曜日) 15:00−17:00
place
理学研究科5号館525  第4講義室
abstract
Recently phase retrieve has been realized based on iterative fast FFTs in optics and X-ray FELs. We further advance this mathematic technique and apply on coherent electron beam, and develop following microscopes for biology: 
・We study basic interaction of low energy coherent electron and atoms.
・We develop new concept of atomic resolution SEM (scanning electron microscope) using digital holography technique on coherent diffraction.
・We perform electron crystallography on nano-crystals of membrane proteins.
・We also participate SACLA Free Electron Laser experiments.
With these atomic resolution microscopes, we will obtain 3D image of atomic structures in DNA, virus, and proteins, in few years.
contact
中家
( t.nakaya@scphys.kyoto-u.ac.jp)
note
GCOEセミナー
title
Femto Second Physics based on Ultrafast Laser Experiments
author
Dr. Keshav Dani 
(沖縄OIST助教)
date
2012年3月2日(金曜日) 15:00−17:00
place
理学研究科5号館525  第4講義室
abstract
In recent years, the ability to synthesize, engineer & observe materials on the nanometer length scale has led to novel phenomena and applications. On the other hand, modern lasers deliver powerful, ultra short pulses of light allowing us to observe the interaction of electrons and atoms on the femtosecond timescale. Together, these technologies allow us to study new paradigms in light-matter interaction - with femtosecond temporal resolution and nanometer spatial resolution. In the Femtosecond Spectroscopy Unit, we will direct these abilities towards two areas of study - (a) Metamaterials & Plasmonics, where artificially nano-engineered materials promise energy-efficient ultrafast photonic devices; and (b) Dirac Materials, where electrons in materials like graphene and topological insulators mimic those found in neutron stars and white dwarfs, leading to intriguing opto-electronic properties.
contact
中家
( t.nakaya@scphys.kyoto-u.ac.jp)
note
GCOEセミナー
title
「中性子のスピン測定における不確定性」-- ハイゼンベルクの不確定性原理を超えて --
author
Yuji Hasegawa 
(Vienna University of Technology, Professor)
date
2012年 2月21日(火曜日) 14:00−16:00
place
理学研究科5号館525  第4講義室
abstract
ハイゼンベルクの不確定性原理は、量子力学の教科書の初めに出てくる基本原理として知られている。 ケンナードやロバートソンによって示された標準偏差を用いた不確定性関係と異なり、測定の誤差と擾乱に関する不確定性関係は証明がなされてなく、ただ「直感的な」関係式として長い間信じられてきた。 最近、小澤によりこの誤差と擾乱に関する不確定性関係が数学的に示された。我々は中性子のスピンの連続測定によってこの小澤によって示された不確定性関係に関する検証を行った。 その結果、ハイゼンベルクによって示された不確定性関係が破れ、小澤の示唆した不確定性関係が成立することが実験的に示された。 この結果はNaturePhysicsに発表され、多くの新聞にも取り上げられた。 今回の講演では、不確定性の実験のみならず、この実験に至るまでの、中性子を使った量子物理の基礎実験を紹介する。
contact
高橋 義朗 (内線:3745)
Yoshiro Takahashi ( yitk@scphys.kyoto-u.ac.jp, ext:3745)
note
GCOE・基研セミナー(宇宙)
title
Gravitational waves from extreme mass ratio inspirals to the 14th post-Newtonian order
author
Ryuichi Fujita
(Universitat de les Illes Balears, Spain)
date
2012/01/25 Wed. 15:30-
place
Seminar Room K202, Yukawa Institute, Kyoto University
abstract
We derive gravitational waveforms needed to compute the 14th post-Newtonian (14PN) order energy flux, i.e. v28 beyond Newtonian approximation where v is the orbital velocity of a test particle, in a circular orbit around a Schwarzschild black hole. We exhibit clearly the convergence of the energy flux in the PN expansion and suggest the fitting formula which can be used for more general orbits around a Kerr black hole. The phase difference between the 14PN waveforms and numerical waveforms after two years inspiral becomes about 10-7for μ/M=10-4 and 10-3 for μ/M=10-5 where μ and M are the masses of a compact object and a supermassive black hole at the centers of galaxies respectively. The 14PN expressions will lead to the parameter estimation comparable to the ones resulting from high precision numerical waveforms for extreme mass ratio inspirals, which are one of the main targets of Laser Interferometer Space Antenna.
contact
note
このセミナーは京都大学基礎物理学研究所と京都大学理学研究科グローバルCOEプログラム「普遍性と創発性から紡ぐ次世代物理学」の共催で行われます。
GCOEセミナー
title
Feedback and teaching in reaction-diffusion information processing
author
Mr. Konrad Gizynski
(Institute of Physical Chemistry Polish Academy of Science)
date
2012年1月16日(月曜日) 13:30−15:00
place
理学研究科 5号館 北棟 第一講義室
abstract
Excitable chemical medium can be applied for information processing. All information processing executed by living organisms is based on chemistry. My PhD project is focused on increasing the flexibility of information processing with reaction-diffusion medium. We plan to design chemical computing systems that are able to modify their functions in the process of learning. In the project we will use Bielousov-Zhabotynski reaction as a computing medium. I am planning to design, build and program an experimental setup within which the state of computing medium can be analyzed. A set of cameras linked to a computer will process images of the medium in the real time. I will investigate different methods (local illumination, local change of electric field, local flows) of influencing the time evolution of the medium and write computer programs that control the applied stimuli.
This feedback will be used as a training tool to teach the medium to perform a selected function. The design of training strategy will be based on procedures similar to those used in genetic programming. It is expected that obtained results will help to determine the structure of the medium for which the process of training can be performed in the most efficient way.
contact
久保善嗣 ykubo@chem.scphys.kyoto-u.ac.jp(内線:3694)
note
       
GCOEセミナー
title
Weyl gravity and Cosmology
author
Dr. Nathalie Deruelle
(APC, University Paris 7)
date
2012年1月10日(火曜日) 15:00 -
place
京都大学基礎物理学研究所 研究棟・講義室K202
abstract
A general framework for the physics of high-intensity beam acceleration in linear accelerators has been developed. Its use in linac design and simulation, its relation to general nonlinear dynamics principles, and application to various contemporary projects such as Accelerator Driven Systems for radioactive waste transmutation, the International Fusion Materials Irradiation Facility, and small neutron sources will be discussed.
contact
佐々木 節 misao@yukawa.kyoto-u.ac.jp(内線:7043)
note
       
GCOEセミナー
title
Space-charge physics design technique for linear accelertors
author
Dr. R.A. Jameson
(Inst. Angewandte Physik, Goethe University Frankfurt)
date
2011年11月28日(月曜日) 14:00−15:00
place
宇治地区・化学研究所・イオン線型加速器実験棟・会議室
abstract
A general framework for the physics of high-intensity beam acceleration in linear accelerators has been developed. Its use in linac design and simulation, its relation to general nonlinear dynamics principles, and application to various contemporary projects such as Accelerator Driven Systems for radioactive waste transmutation, the International Fusion Materials Irradiation Facility, and small neutron sources will be discussed.
contact
岩下芳久 iwashita@kyticr.kuicr.kyoto-u.ac.jp, 17-3282
note
       
GCOEセミナー
title
Lack of inversion symmetry in heavy fermion and simple metal superconductors
author
Friedrich Kneidinger
(Technische Universitat Wien)
date
2011年10月31日(月曜日) 17:15 - 18:45
place
物理学教室 401号室
abstract
Superconductors which do not have a center of inversion according to their space group are generally summarized as non-centrosymmetric (NCS) superconductors. The lack of inversion leads to an electrical field gradient which emerges in an antisymmetric spin-orbit-coupling of the so called Rashba type. Furthermore this triggers a splitting of the Fermi surface, thereby lifting the spin degeneracy. In theory this leads to a superposition of spin singlet as well as spin triplet state Cooper pairs. One material which shows NCS superconductivity as well as heavy fermion behavior is CePt3Si. This material shows various interesting features like a coexistence of AFM and superconductivity and an extraordinarily large upper critical field. The latter in combination with measurements of the Knight shift leads to the assumption of a mainly spin-triplet Cooper pairs in the SC condensate. Another class of materials are simple ternary intermetallics with a lack of inversion center. Promising candidates are BaPtSi3, SrPdSi3 and SrPtGe3. These candidates exhibit a conventional metallic behavior above Tc according to a Bloch-Gruneisen like resistivity. Measurements of the specific heat, which follows the Muhlschlegel model, and μSR- measurements which do not show time reversal symmetry breaking, strongly indicate a spin-singlet BCS-like Cooper pairing. Another interesting example is the ternary 111-type like LaPtSi which crystallizes in the I41md space group. This material shows SC at 3.3 K and a large upper critical field which refers to a non- vanishing contribution of spin triplet Cooper-pairs.
contact
Yoshi Maeno maeno@scphys.kyoto-u.ac.jp,ext. 3783
note
       
GCOEセミナー
title
Vortex molecules in thin films of layered superconductors
author
Professor Alexandre Buzdin
(University of Bordeaux, France)
date
2011年10月26日(水)15:30〜
place
物理学教室 401号室
abstract
Both the equilibrium and transport properties of the vortex matter are essentially affected by the behavior of the intervortex interaction potential. In isotropic bulk superconductors this potential is well known to be repulsive and screened at intervortex distances R greater than the London penetration depth λ. As a result, in perfect crystals quantized Abrikosov vortices form a triangular lattice. In thin films of anisotropic superconductors this standard interaction potential behavior appears to be strongly modified because of the interplay between the long-ranged repulsion predicted in the pioneering work by J. Pearl and the attraction caused by the tilt of the vortex lines with respect to the anisotropy axes. This interplay results in a new type of vortex arrangement formed by finite-size vortex chains, i.e., vortex molecules. Tilted vortices with such unusual interaction potential form clusters with the size depending on the field tilting angle and film thickness or/and can arrange into multiquanta flux lattice. The magnetic flux through the unit cells of the corresponding flux line lattices equals to an integer number N of flux quanta. Thus, the increase in the field tilting (or varying temperature) should be accompanied by the series of the phase transitions between the vortex lattices with different N. The similar scenario should be realized in strongly anisotropic BSCCO high Tc superconductors where in tilted field a crossing lattice of Abrikosov vortices and Josephson vortices appears.
contact
固体電子物性 松田祐司 (内線 3790)
note
       
GCOEセミナー
title
The Sun as a laboratory for quantum physics
-Enigmatic scattering polarization of NaD1 observed in the Sun -
author
Dr. Jan Stenflo
(チューリッヒ工科大学名誉教授)
date
2011年10月 25日(火曜日) 9:30−11:00
place
宇宙物理学教室 4号館5階会議室(531号室)
abstract
The Sun has often been referred to as a Rosetta stone for astrophysics, since its proximity allows us to explore in detail the fundamental processes that govern the physics of objects in distant parts of the universe. Among these fundamental processes there was little attention given to polarization phenomena until about a decade ago, apart from various applications of the standard Zeeman effect for magnetic field diagnostics. With the implementation of new, highly sensitive imaging Stokes polarimeters a new and previously unfamiliar face of the Sun has been revealed, in the form of the richly structured Second Solar Spectrum. Its spectral structures are exclusively due to coherent scattering processes, which are modified by the partial decoherence caused by magnetic fields via the Hanle effect. The observed polarization phenomena are signatures of a rich variety of quantum-state superpositions, which in a unique way reconnects astrophysics with fundamental aspects of quantum theory. Here I choose to address this topic from a personal perspective, starting with some biographical notes and ending with some ideas on how current quantum scattering theory may need to be extended to explain the enigmatic polarization observed in the D1 lines of sodium, barium, and potassium.
contact
一本 潔  ichimoto@kwasan.kyoto-u.ac.jp 0578-86-2311
note
       
GCOEセミナー
title
Implications of genuine gauge invariance and inflationary vacua
author
Dr. Yuko Urakawa
(University of Barcelona, Ochanomizu university)
date
2011年10月17日(月曜日) 16:30−17:30
place
基礎物理学研究所 研究棟・会議室K206
abstract
The conventional cosmological perturbation theory has been performed under an assumption that we can access the whole spatial region of the universe. This is, however, not the case in actual observations because observable region is a portion of the whole universe. To give a theoretical prediction to the observable fluctuations, gauge-invariant observables should be composed of information in our local observable universe with finite volume. In this talk, I will survey implications of the gauge invariance in the local universe, highlighting differences from results in the conventional perturbation theory. Interestingly, requesting the gauge invariance in the local universe may tell us about allowable initial states in inflationary universe.
contact
Takahiro Tanaka (tanaka@yukawa.kyoto-u.ac.jp)
note
       
GCOEセミナー
title
Application of Wainwright’s Formalism to Anisotropic Inflation
author
Dr. Kei Yamamoto
(University of Cambridge)
date
2011年 10月18日(火曜日) 13:30−15:30
place
基礎物理学研究所 研究棟・会議室K206
abstract
Recently attempts have been made to extend the scope of inflationary model building from conventional scalar-dominating scenarios to including more general energy components such as vector fields. While isotropy of the background space is often taken for granted, it is necessary to abandon the FLRW model in order to fully incorporate the anisotropic nature of the fields. In this talk, I describe a systematic construction of dynamical systems for the anisotropic cosmological models, which was developed by John Wainwright. The use of vierbeins results in a unified treatment for all the different structures of spatial curvature. After normalizing the variables by Hubble expansion rate, to look for potential self-similar attractor solutions reduces to an algebraic problem. Then I apply this mathematical framework to a certain type of Lagrangian for Maxwell and Kalb-Ramond fields coupled to a dilaton and discuss “pseudo-no-hair” conjecture within this class of inflationary universes.
contact
早田 次郎 jiro@tap.scphys.kyoto-u.ac.jp
note
       
GCOEセミナー
title
research activities on superconducting qubits
author
吉原 文樹
(独立行政法人 理化学研究所 基幹研究所 研究員)
date
2011年 8月4日(木曜日) 11:00−12:00
place
理学研究科5号館115号室
abstract
磁束量子ビットは数マイクロメートル角の超伝導ループおよび、数百ナノメートル角の4つのジョセフソン接合から構成されている。 セミナーの前半では我々のグループ紹介なども交えながら、磁束量子ビットの作成方法、動作原理および測定方法を説明する。 セミナーの後半では、強くドライブした磁束量子ビットのラビ振動の測定結果について報告する
contact
高橋 義朗 (内線:3745) yitk (at) scphys.kyoto-u.ac.jp
note
       
GCOE・ミニワークショップ(アウトリーチ委員会)
タイトル
出前授業等経験交流ミニワークショップ
日時
2011年6月21日(火) 15:00 - 17:30
場所
理学部4号館 5階504号室 (会議室)
趣旨
この度、GCOEアウトリーチ委員会では、出前授業や市民講座等での 経験をお互いに交換することによって、アウトリーチ能力の向上を図ろう という趣旨で、下記の要領でミニワークショップを試行的に開催して みようということになりました。
それぞれの体験にもとづき、このような話を小学生(あるいは中高生でも一般対 象でも)にしたら誤解されたのでこう説明すればよかった、 わかりやすくするために例え話を入れたら思いもよらぬ驚きの誤解をされていた、 これ位はわかっているだろうと思って話をしたらそうではなかったとか、 逆に、こうするとよかった等等といった具体的体験談をお互いに披露しあって、 互いの能力の向上を図ろうという趣旨です。 多分に放談的あるいは個別技術的になるかもしれませんが、 このような事例の積み重ねから普遍的な視点がでてくる可能性もあり、 まずはどの程度のことができるのかということで、試行的に開催して みようという次第です。
プログラム
15:00-15:10 太田耕司(アウトリーチ委員会)
 このワークショップについて  (pdf)
15:10-15:30 柴田一成(天文台、アウトリーチ委員会)
 出前授業:私の経験 (pdf)
15:30-15:50 森谷友由希(宇宙物理)
 私の体験から (pdf)
15:50-16:10 信川正順(次世代研究者育成センター、物理2(連携))
 出前授業等の活動 (pdf)
16:10-16:25 休憩
16:25-16:45 磯部洋明(宇宙ユニット)
16:45-17:05 常見俊直(理学研究科社会連携室)
 出前授業等経験交流 ミニワークショップ (pdf)
17:05-17:30 全体討論、今後の展望等
contact
GCOEアウトリーチ委員会 太田耕司
GCOE・基研セミナー(素粒子)
title
Bulk-boundary resonance in one matrix model and Liouville gravity
author
Jean-Emile Bourgine
(CQUeST, Sogang University)
date
2011 年6 月15 日(水) 1:30 p.m.
place
京都大学基礎物理学研究所 湯川記念館・会議室Y306
abstract
The issue of relating discrete and continuous descriptions of a QFT will be discussed within the solvable example provided by the 2D Quantum Gravity. Here, a continuum limit for the discrete description, given by the hermitian matrix model, can be performed. Results should be compared with the Minimal Liouville Gravity, a minimal model matter coupled to the Liouville field theory. Effective comparison of the correlation functions requires the introduction of a finite renormalization of the couplings, known as the ’resonance transformation’. This transformation will be investigated at the level of boundary 2-pts and bulk-boundary correlators. In the process, the construction of matrix model boundaries will be reviewed.
contact
基礎物理学研究所 准教授 笹倉 直樹(内線:7037)
note
京都大学基礎物理学研究所と京都大学理学研究科グローバルCOEプログラム「普遍性と創発性から紡ぐ次世代物理学」の共催で行われます。
*参照 基研HP: http://www.yukawa.kyoto-u.ac.jp/contents/seminar/detail.php?SNUM=51215
GCOE・基研 集中講義(宇宙)
title
Effective Action in Non-trivial Background
author
Sang Pyo Kim
(Kunsan University)
date
2011年5月24日(火) 14:00-15:30, 15:40-17:10, 5月25日(水) 10:30-12:00
place
基礎物理学研究所 研究棟・会議室K206
abstract
The Schwinger variational principle has been known as one of two formalisms of quantum field theory, the other being the Feynman functional integral. The principle has been further developed by B. DeWitt such that it can be applied to systems with nonstationary backgrounds, external gauge fields and or curved spacetimes. In the first lecture, the covariant formulation of canonical quantum field theory will be introduced based on the Schwinger variational principle and the Peierls brackets and the principle will be employed in calculating the effective actions in terms of either Green's function or Bogoliubov coefficient. In the second lecture, the effective actions in terms of the Bogolioubov coefficient will be applied to fermions and bosons coupled to some configuration of electromagnetic fields and the physical aspects of the nonperturbative effective actions will be investigated. In the third lecture, the method will be applied to curved spacetimes such as a de Sitter space and a Schwarzschild black hole and physical interpretations and perspectives of the nonperturvtive effective action will be addressed.
contact
基礎物理学研究所 教授 佐々木 節(内線:7043)
note
京都大学基礎物理学研究所と京都大学理学研究科グローバルCOEプログラム「普遍性と創発性から紡ぐ次世代物理学」の共催で行われます。
*参照 基研HP: http://www.yukawa.kyoto-u.ac.jp/contents/seminar/detail.php?SNUM=51190
GCOE・基研 集中セミナー(素粒子)
title
Brane Tilings and the mesonic moduli space of Ypq Theories
author
Rak-Kyeong Seong
(Imperial College London / YITP)
date
2011年05月11日(水) 13:30〜
place
基礎物理学研究所 湯川記念館・会議室Y306
abstract
Brane Tilings form a large class of superconformal field theories in 3+1d and 2+1d. In this talk, I will discuss a particular set of models known as Ypq theories in 3+1d. I discuss how the mesonic moduli space of these theories is characterized by a generating function of chiral gauge invariant operators known as the Hilbert series. I will illustrate how from the brane tiling construction certain limits in the parameter space lead from Ypq theories to abelian orbifold theories.
contact
基礎物理学研究所 准教授 笹倉 直樹(内線:7037)
note
京都大学基礎物理学研究所と京都大学理学研究科グローバルCOEプログラム「普遍性と創発性から紡ぐ次世代物理学」の共催で行われます。
*参照 基研HP: http://www.yukawa.kyoto-u.ac.jp/contents/seminar/detail.php?SNUM=51196

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