Theoretical Particle, Nuclear, Astrophysics Group

Professor: Y. Fujita (Theoretical Astrophysics)
Associate Professor: W. Yin (Particle Theory)
Associate Professor: Dr. Rer. Nat. Habil. S.V. Ketov (High-Energy Theoretical Physics)
Associate Professor: T. Hyodo (Nuclear Hadron Physics)
Assistant Professor: N. Kitazawa (Particle Theory)
Assistant Professor: S. Sasaki (Theoretical Astrophysics)

Particle physics is a discipline that aims to reveal the depths of the structure of matter in our universe. The Elementary Particle Theory Subgroup vigorously pursues research on a wide range of topics through collaborative research with overseas researchers. Among the topics we address are the implications of the infinitesimal neutrino masses that were discovered by the Super-Kamiokande experiment and, very recently, the KamLAND experiment; experimental exploratory methods for understanding the overall structure of lepton flavor mixing; theoretical study that focuses particularly on the use reactor neutrinos; the origin of the masses of fundamental particles, which have a large hierarchy of five orders of magnitude; and attempts to arrive at a unified theory, which have made remarkable progress in recent years. (Particle Theory)
The Theoretical High-Energy Physics Laboratory explores the theory of elementary particle strings and their supersymmetry. String theory, including quantum gravity theory, is considered to be the only theory that makes possible a unified understanding of elementary particles to the universe’s creation. Supersymmetry is a fundamental symmetry between particles obeying different statistics. A consistent string theory is possible only if this symmetry is satisfied. We conduct our research carried out in collaboration with research teams in the United States, Germany, Russia, and other countries.(High-Energy Theoretical Physics)
Hadrons such as protons, neutrons, and pions are composed of quarks and gluons by the strong interaction, which is one of the four fundamental forces in Nature. Hadrons further combine to form atomic nuclei. The strong interaction is inherently different from gravitational and electromagnetic forces, and its actual phenomena cannot be calculated directly from the fundamental theory. Consequently, various ideas and methods have been developed in research. The Nuclear Hadron Physics Subgroup conducts theoretical research on the exotic states of hadrons, which reflect the non-perturbative nature of the strong interaction, as well as on nuclei as finite quantum many-body systems.(Nuclear Hadron Physics)
The Theoretical Astrophysics Subgroup explores questions concerning the makeup of the universe, including formation and evolution of galaxies and galaxy clusters, as well as high-energy phenomena involving neutron stars, black holes, and supernovae based on electromagnetism, fluid mechanics, the theory of relativity, and other areas of fundamental physics. We also study the fundamental physical processes, such as particle acceleration and X-ray and γ-ray radiation, as the basis for these studies. Although our approach is mainly theoretical, we actively test our theoretical predictions using the latest observations. We also make our own observations when necessary.(Theoretical Astrophysics)

Nonlinear Physics

Professor: A. Shudo / Assistant Professor: A. Tanaka

The objective of nonlinear physics is to elucidate the mathematical structures common to the nonlinear world, and to develop new methodologies for analyzing complex systems. In the Nonlinear Physics Group, we specifically study nonlinear dynamics, focusing on the problem of chaos in dynamical systems. In particular, we explore the role of chaos in classical and quantum mechanics in nonintegrable systems, for which no analytical solution can be obtained.

Quantum Condensed Matter Theory

Professor: H. Mori / Associate Professor: E. Arahata / Assistant Professor: H. Otsuka

Every material around us is composed of countless atomic nuclei and electrons. Because particles interact with each other, they exhibit various properties that cannot be predicted from the individual particles. Condensed matter physics research aims to understand and systematize this phenomenon based on statistical thermodynamics and quantum mechanics and then predict new properties. In the Quantum Condensed Matter Theory Group, we focus on various phenomena related to such many-body effects and conduct research to shed light on their micro-level mechanisms and macro-level characteristics. Specifically, we study critical phenomena, low-dimensional quantum systems, cooled atomic gases, Bose-Einstein condensation, superfluidity, superconductivity, and other topics using analytical and computational physics methods. We also explore possibilities for applying machine-learning techniques to these problems.

Strongly Correlated Electron Theory

Professor: T. Hotta / Associate Professor: K. Hattori / Guest Professor: K. Kubo (Cooperative Graduate School Education: JAEA)

The properties of matter―in other words, physical properties―are incredibly diverse. It might seem at first glance that there is no way to understand them in a unified manner. However, many years of research have revealed that physical properties can be understood in a unified manner if one starts with the hierarchy of atoms and electrons. Condensed matter physics is the study of physical properties in this way, and condensed matter theory constructs theories concerning physical properties with reference to experimental evidence, particularly using calculation as its means. In our laboratory, the Hotta-Hattori Lab, we conduct theoretical studies of magnetism and superconductivity in strongly correlated electron materials, such as transition metal compounds, rare earth compounds, and actinide compounds, by analyzing many-body electron systems in which the interaction among electrons plays an intrinsically important role using field theory and numerical calculation.

Computational Materials Science

Associate Professor: T. Nomoto

Experimental High Energy Physics

 Professor: H. Kakuno / Assistant Professor: T. Kumita / Guest Professor: I. Adachi / Guest Professor: S. Nishida (Cooperative Graduate School Education: KEK)

As a participant in international research undertakings, the Experimental High Energy Physics Laboratory is conducting the super B-factory experiment (Belle-II) using a electron-positron collider (SuperKEKB) at KEK, Tsukuba, and a long baseline neutrino oscillation experiment (T2K) using neutrinos generated at J-PARC accelerator and detected at a water cherenkov detector Super-Kamiokande, and a particle experiment (ATLAS) using world’s largest hadron collider (LHC). Through these experiments, we are engaged in cutting-edge research to illuminate the ultimate structure of matter and differences between the matter and antimatter worlds. Our research projects also include R&D of particle detectors that are used for those experiments. We also conduct small-scale student-led experiments using TMU’s facilities. Such experiments include explorations for positronium rare decay events.

Atomic Physics

Professor: H. Tanuma / Assistant Professor: S. Iida / Guest Professor: T. Azuma (Cooperative Graduate School Education: RIKEN)

Atomic physics deals with the structure and dynamic processes of the micro-scale atoms and molecules that form the basis of various natural phenomena. The Atomic Physics Laboratory uses independently developed equipment to perform collision experiments with various ion beams. We actively pursue research in a broad range of fields. Here are just a few examples. We reproduce the X-ray radiation produced in space by ions in the solar wind by stripping electrons from atoms with 1-million-degree plasma to create multicharged ions. We investigate the properties of interstellar molecular ions using a device that can control the motion of ions using only an electric field and accumulate them in a 7.7-meter orbit. We make ions drift at extremely low speeds in ultracold gases to achieve low-energy collisions of about 1 meV. And, in a joint research project with RIKEN, we use an off-campus accelerator to observe the resonant excitation that occurs when fast heavy ions (traveling at about 70% of the speed of light) pass through a crystal.

Experimental Astrophysics

Professor: Y. Ezoe / Associate Professor: Y. Ishisaki / Assistant Professor: K. Ishikawa
 / Guest Professor: M. Ishida (Cooperative Graduate School Education: JAXA)

How did the universe evolve and how did the stars and galaxies form? To answer these questions, the Experimental Astrophysics Laboratory is observing the universe with X-rays and γ-rays and developing new observation instruments for installation on scientific satellites. Our focus ranges from astronomical objects (including space-time singularities and black holes) to galaxy clusters dominated by dark matter. We also conduct joint research with the Cosmology Group. In the area of technology development, we developed instruments for the Suzaku satellite that was launched in 2005, an X-ray microcalorimeter that operates at extremely low temperatures, and a thin plate X-ray reflecting telescope with high light gathering power.

Soft Matter

Professor: R. Kurita 

Soft matter is widely used in various industrial fields, such as liquid crystal displays, tires, plastics, and pharmaceutical capsules, as well as in products used in daily life, such as foams and mayonnaise. However, research on soft matter has been mainly empirical, and a systematic understanding of it has yet to be achieved. In particular, very little research has been undertaken in near real-world conditions, such as under spatial inhomogeneity (i.e., differences in temperature and pressure). For this reason, the Soft Matter Laboratory is studying the physical properties of soft matter under spatial inhomogeneity to elucidate its mechanisms and discover structures that will be the basis of new functional materials.

Correlated Electron Physics

Professor: Y. Aoki / Professor: T. Matsuda / Assistant Professor: R. Higashinaka

Some materials exhibit interesting behaviors that cannot be predicted from the properties of individual electrons alone due to the strong interactions among the many electrons that make up the system. Such materials are called strongly correlated electron systems. The Correlated Electron Physics Laboratory’s focus ranges from new types of superconductivity, ordering of electron orbitals, local oscillation and frustration of caged atoms in filled skutterudites and other novel compounds to spin-dependent conduction phenomena in microscopic magnetic materials fabricated by nanotechnology. Starting from the development of pure new materials, we aim to explore new physical properties and explain their mechanisms by measuring electronic properties down to extremely low temperatures and making full use of neutron X-ray scattering at off-campus facilities as well as strong magnetic field experiments.

Superconducting Materials

Associate Professor: Y. Mizuguchi / Assistant Professor: A. Yamashita 

The Superconducting Material Laboratory explores new materials and studies physical properties in such areas as superconductors and thermoelectric conversion materials. Our aim is to develop novel functional materials that will be critical in solving our energy problems. Placing particular focus on layered metal chalcogenides, we design and synthesize new materials using high-pressure synthesis, chemical pressure, and other special techniques. To shed light on the mechanisms of superconductivity and improved thermoelectric performance, we investigate physical properties under multi-extreme conditions and conduct crystal structure analyses using synchrotron radiation facilities in Japan and abroad. We also actively participate in international collaborative research.

Surface and Interface Physics

Professor: K. Yanagi

The nanoscale is an extraordinarily unique realm bridging the micro-level world of molecules and atoms and the macro-level world that is easily manipulated by humans. Materials with ordered structures at the nanoscale exhibit novel properties that cannot be seen when their compositional elements are in disorder. Carbon nanotubes and photosynthetic pigment-protein complexes are examples of such materials. In the Surface and Interface Physics Laboratory, we conduct our research with interest in the properties that first appear at the nanoscale as well as the properties that appear when nanomaterials form higher-order assemblies. We also develop technologies that will be necessary for understanding and controlling these properties. We produce and purify extremely pure nanomaterials and then study their physical properties primarily with laser spectroscopy and other spectroscopic methods.

Nano-science Research

Associate Professor: Y. Miyata / Assistant Professor: Y. Nakanishi 

The Nanoscience Research Laboratory’s research focuses on materials science. We explore nanomaterials with unique low-dimensional structures, such as one-atom-thick two-dimensional sheets, nanotubes, and nanowires represented by graphene and carbon nanotubes. We also study heterostructures formed by the joining of different nanomaterials and their interfaces as well as atoms and molecules bound in nanospace. We are endeavoring to explain physical properties and exploring their applications using a variety of experiment-centered methods (material exploration using vapor phase growth, device production using microfabrication techniques, Raman scattering, light absorption and emission, electrical conduction, photoelectric conversion, thermoelectric conversion, scanning probe microscopy, electron microscopy, X-ray diffraction, technologies for measuring magnetic susceptibility and the like, first principle analysis, and molecular dynamics simulations).