Particle and Nuclear Theory
The subjects of particle physics are the elementary particles – the most basic constituents of matter – and their interactions – the most fundamental law of Nature. Particle physics is also called high energy physics since the short-distance physics corresponds to the high-energy physics because of the uncertainty principle in quantum mechanics.
Nuclei are quantum mechanical many-body systems which consist of protons and neutrons. As they are self-bound systems with finite number of constituents, many rich and complex phenomena have been known to occur there. One of the primary goals of nuclear physics is to address them starting from the nucleon degrees of freedom.
Condensed Matter Theory
Experimental Nuclear and Particle Physics
Collision of electron and positron at high energy can produce various heavy particles such as B mesons and, in the future, possible Higgs bosons and new particles that may signal entirely new theory of physics.
The Nature and the Universe provide us with a good laboratory for experiments on particle physics. A plenty of elementary particles are flying around us, some of which have the information of the birth and the evolution of the Universe, and others are continually emitted from the Galaxy, the Sun and the Earth and coming to the ground. The purpose of non-accelerator experiments is to detect these particles and study their characteristics and the Universe.
Thanks to recent progresses of accelerator techniques, the frontier of the nuclear science is rapidly expanding. Fig. shows some topics of the modern nuclear physics. Now it becomes possible to produce and experimentally study various exotic nuclei under extreme conditions. Our way of understanding materials is rapidly changing due to recent progresses of those studies.
Research Center for Electron Photon Science (ELPH), a university-based laboratory, is a Joint/Usage Research Center approved by the Ministry of Education and Science. It aims to promote fundamental researches and applications in nuclear science as well as to educate students and young researchers over the framework of a university. ELPH operates a high intensity 60 MeV electron linear accelerator (LINAC)and a synchrotron currently boosting electrons injected by an injector LINAC from 90 MeV to 1.3 GeV.
The nuclear radiation physics group consists of the accelerator research and instrumentation research divisions of the Cyclotron and Radioisotope Center (CYRIC) founded for multi-purpose use of a cyclotron and for handling of high-level radioisotopes.
Condensed Matter Experiment I
We study the electronic structure of strongly correlated electron materials such as high-temperature superconductors with ultrahigh-resolution angle-resolved photoemission spectroscopy (ARPES). ARPES is a unique and powerful experimental technique to directly observe the momentum-resolved electronic structure. We have constructed an ultrahigh-resolution ARPES spectrometer in our laboratory and the present energy resolution is in the world-best level.
We are currently studying nano size materials comprised of IVth-group elements of C, Si, Ge and Sn, for achieving new insights to fundamental understanding in solid state physics of nano materials, as well as development of advanced electronic devices in the next generation.
Low Temperature Quantum Physics Group performs the experimental researches in condensed matter physics at very low temperatures, in high magnetic fields and under high pressures. Besides the developments of new techniques and detection systems under such extreme conditions, synthesis of novel materials and growth of high quality single crystals are other major activities of the group.
When a macroscopic number of electrons are strongly correlated with each other, a novel quantum state characterized by the symmetry breaking and/or topological anomaly frequently emerges. Examples include superconductivity, spin liquid, and quantum Hall effect. Elementary excitations from such quantum state are completely different from one electron itself.
Highly correlated electron systems in 5f-, 4f- and 3d-compounds as well as low-dimensional organic compounds show various interesting physical properties such as metal-insulator transition, valence fluctuation, heavy-electron behavior, multipolar ordering and lowdimensional quantum spin behavior.
Our group investigates electrodynamics of water molecules, protons, electrons, ions, biological molecules confined in various types of nanospaces such as one-dimensional channels, two-dimensional narrow spaces and cage spaces. The electrodynamics is an interdisciplinary subject associated with biochemistry, medical and environmental science and energy problems, etc. Now we focus on the following subjects.
In strongly correlated electron systems, new phenomena can appear due to a complex combination of degree of freedom of the electron (charge, spin and orbital). To understand the mechanism, for instance, high Tc superconductivity, low dimensional quantum spin phenomena, electronic charge segregation and so on, it is quite important to obtain the information of not only basic structure but also the dynamics of materials with strong electron correlations.
We have investigated a variety of physical phenomena of condensed matters in strong magnetic fields. One of main subjects is the quantum magnetism in nano-scale molecular complex clusters. The discreteness of the energy levels of those clusters leads to the novel non-equilibrium dynamics such as non-trivial quantum oscillation.
Our group studies low-temperature electrical properties of various superconductors and highly-correlated magnetic materials, such as transition metal oxides, iron-based pnictides, and Ce-based-compounds.
The main research subjects in this group are the experimental investigations of the organic molecular conductors. The characteristic properties of the organic materials are multiple flexibilities owing to the assemble structure of nanometer-size molecules.
The research subject in this division is a further development of functionalities at the solid interfaces. In particular, we aim to discover a novel function at the well-regulated and abrupt interfaces prepared by our thin film growth techniques.
Condensed Matter Experiment II
We are interested in the physics at surfaces, interfaces, nanostructures and other novel low dimensional structures, where electrons behave quite differently from electrons in the bulk. We have three ongoing projects.
The purpose of this laboratory is to investigate the physical background of the cellular life from a material science point of view. We adopt two approaches “Soft Matter Physics” and “Biophysics” to reach our goal.
Our laboratory consists of two subgroups: the "Photonic crystals and metamaterials" group explores novel physics in artificial periodic structures in the scale of or much smaller than the light wavelength, and the other group studies "ultrafast phenomena in conjugated π-electron systems", such as light-harvesting complex systems and carbon nanotubes, by developing advanced femtosecond, nonlinear spectroscopic techniques.
In the area of quantum semiconductor physics, interesting research has been progressing based on semiconductor hetero- and nano-structures with the concept of carrier interaction. It has been found that two-dimensional systems show fruitful quantum Hall properties depending on orbital, spin and valley degrees of freedom.
Our research group is aiming at the ultrafast optical/THz manipulations of corrective electron and spin motions in solids by using advance light source such as mono-few optical cycle IR pulss and THz pulse.
In magnetic materials, novel physical properties are emergent when the crystal and/or spin structure are peculiar in terms of topology or symmetry. Such physical properties may give rise to useful material functions. This research group studies the emergent material functions induced by topology or symmetry breaking in magnetic materials.
We investigate solid surfaces and interfaces at atomic level in order to create surfaces and interfaces with various functions. We have developed several original techniques for surface analysis, such as correlated thermal diffused scattering (CTDS) and Weissenberg reflection high energy electron diffraction (WRHEED).
Due to their very large quantum fluctuations, electron spins sometimes show quite intriguing and largely fluctuating ground states at low temperatures. Such fluctuating ground states may be enhanced by geometrical frustration, low dimensionality, and/or coupling to other degrees of freedom. We are aiming at understanding such fluctuation-dominated ground states, and also at finding novel macroscopic quantum phenomena due to the quantum fluctua- tions, using neutron inelastic scattering.
Crystal symmetries, microscopic crystal structures, atom positions, Debye-Waller factors and bonding charge distribution are studied by convergent-beam electron diffraction (CBED) and electron microscopy using an energy-filter transmission electron microscope...
We are studying the application of quantum mechanical phenomena to high performance sensing technique. Photon Factory at KEK (Tsukuba) offers materials structure research with synchrotron radiation. RIKEN Advanced Research Institute conducts Terahertz(THz)-wave research and development at Sendai facility. NTT Basic Research Laboratories are studying ultrasmall force and displacement detection using a small bar called as a micromechanical resonator.