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Entering the unknown and the unexplained

Understanding the fundamental elements of matter

A good way to understand elementary particles, which are the smallest building block composing matter, would be to take a step away from your perception of the particles that are visible to you. Mathematical formulae - and your imagination - are the key means for understanding how elementary particles behave, and this also allows us to theoretically predict the existence of new elementary particles. The existence of the Higgs boson has been predicted as an elementary particle that gives mass to elementary particles, and its existence is about to be ascertained by accelerator experiments.
There are many aspects in elementary particles which have not been explained yet. The development of a theory that encompasses and integrates all theories on elementary particles is still awaited.


Footprints of the creation of matter left on atomic nuclei

The origin of atomic nuclei - consisting of protons and neutrons - goes back to the Big Bang. Presently, about 2,000 nuclides are known to exist, but it is not known how nuclei have been created with this variety.
Research on atomic nucleus is expected to be applied to wide-ranging areas, from medical technology development to resolutions of energy issues.

Electronic state detection with nuclear spins

Physical properties of materials essential to our lives - such as conductivity and magnetism - are generated by electrons in solids. Electrons in solids interact with nuclear magnetisation (atomic size magnets), and observation of the state of nuclear magnetisation allows for microscopic observations of electron systems. With nuclear magnetic resonance (NMR) spectroscopy, states of nuclear magnetisation are detected as the modification of the resonant frequencies with radio frequency fields. Wide applications are found in medical technologies such as MRI and drug discovery and also in chemical analyses.

Observe, pick up, and control an atom

A scanning tunneling microscope (STM) is an instrument which enables us to observe atomic structures on the surfaces of materials such as metals and semiconductors. This microscope has helped to achieve progress in atomic-level studies of the atomic and/or electronic structures of various materials, for example, the spatial dependence of energy gap in high-Tc cuprate superconductors, which is strongly inhomogeneous on a nano-meter scale. Furthermore, the fundamental technique of atomic manipulation using STM has been studied extensively; it can control the positions and array of atoms on crystal surfaces.

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Distinct properties of systems with a huge number of particles

Many-particle systems are ubiquitous around us: water with 6×1023 H2O molecules per gram; air composed of oxygen and nitrogen molecules; and electrons in metals that carry electricity. These systems can exist in different "phases" like ice, water, and vapor of H2O molecules, and different phases are separated by "phase transitions" that often accompany "broken symmetries", e.g., the one between ice and water. Moreover, they usually exhibit some distinct features, e.g., "superconductivity" of metals without electrical resistance and "ferromagnetism" of iron. We study phenomena characteristic of many-particle systems based on quantum mechanics, statistical mechanics, and quantum field theory.

Toward room temperature superconductivity

The electrical resistance of certain metals becomes zero at extremely low temperatures. This phenomenon is called superconductivity - known for over a century - and it had been thought that superconductivity occurs only below 30K (-243C). Later, it was discovered that superconductivity occurs in new materials made of organic matter or oxides. Today, superconductivity is observed in certain materials at temperatures as high as 138K (-135C). These organic superconductors and oxide superconductors are thought to be realised by a mechanism different to conventional superconductivity. When that mechanism is established, room temperature superconductivity will no longer be a dream.

Electrons 1,000 times heavier than usual

Electron mobility in a crystal calculated in terms of mass is called the "effective mass of electrons". In alkali metals, which have good electrical conductivity, the effective mass of electrons is about the same as the value expected from the free-electron theory. On the other hand, with the inter-metallic compounds containing elements of rare earths (Ce, Pr, Yb, etc.) or actinides (U, Np, etc.), there is a group of materials which has an effective mass several hundreds to a thousand times greater than the free-electron mass, due to the interactions between electrons that exist in large numbers. This group of materials is called "heavy-electron (heavy-fermion) systems". Our group investigates magnetic properties of the heavy-fermion materials using very-low-temperature experimental techniques and microscopic measurements such as neutron scattering and muSR.

New magnetism realised and controlled in nanoscale

We conduct research on magnetism and electron spin physics of solids, mainly for surfaces, ultra-thin films, and nano-structured materials, where the key words are "spin" and "nano". When materials become smaller or thinner, novel magnetic and spin-related properties appear because of broken symmetry. In experiments, we use Spin-Polarized Scanning Electron Microscope (Spin SEM), Spin-Polarized Scanning Tunneling Microscope (STM), Spin-Polarized Spectroscope, 4 Probe with SEM/STM, Physical Property Measurement System, etc., which we have developed or modified for our own use.

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Life as an aggregation of liquids

From the viewpoint of molecular motion it is relatively easy to understand the gas phase with molecules in free flight and the solid phase with vibrating molecules regularly arranged in crystalline lattice. On the other hand, it is very difficult to understand the liquid phase with molecules changing their positions from place to place and interacting with each other.
Living organisms are constructed with liquid throughout their cells. Research into liquids is an important area in physics and also leads to understanding of the process of life and its origin from basic principles.

Explore the wonders of physical phenomena with the aid of laser

Light is a type of electromagnetic wave and interacts with charged particles (electrons and atomic nuclei) in materials. When the electromagnetic wave induces charged particles to oscillate, we observe "light absorption". When oscillations of the charged particles cause an electromagnetic wave, we observe "light emission". When these two phenomena occur simultaneously, we observe light being scattered, reflected, or refracted.
Optical physics deals with these phenomena, trying to establish a unified theory of them. With laser irradiation, which has high intensity and high temporal resolution, we are researching, amongst others, a phenomenon where a particular type of matter absorbs a certain type of light and then emits a different type of light, and a phenomenon where electric conductivity changes.

Materials with custom-made qualities

When a material is produced from several substances, each in certain proportions, you may find properties you would never expect to find in that material. A case in point is semiconductors, which have distinct properties of being able to control current. "Ferroelectrics" is another example, which is currently drawing strong attention. The development of ferroelectrics that are highly functional and conducive to the development of a next-generation memory is anticipated.

Finding out common properties among networks

It is possible to discover commonalities between networks in terms of how each constituent element is connected to others, be it a network in the natural world or one in the man-made world, e.g., human relations, the internet, electrical grid, and food chains. As an example, there is a phenomenon known as the "small world phenomenon", in which you may reach anybody in the world by contacting a friend of yours, then contacting a friend of your friend, and repeating this process several times. Statistical physics researches networks and has been finding common properties between these networks.

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To answer the question of the birth of a star in the Milky Way

The Milky Way is a huge collection of 100 billion stars called the Galaxy. We know that in the Galaxy one star forms each year, but we do not know very well how this occurs. Revelation of the mystery is attempted by observing emission lines from carbon monoxide molecules, ammonia molecules, and water molecules with radio telescopes and by analysing the gas at an extremely low temperature of 10K (-263C). These radio waves from the universe give us a clue to answering the question as to how stars are born.

Looking into matter with computers

Physics is a discipline that requires you to observe and think. Observation is followed by interpretation, and prediction is followed by examination. This twosome of theorising and experimenting is central to scientific investigations into natural phenomena. An addition to this twosome is an emerging and rapidly advancing third approach called "computational physics", which has been realised thanks to the remarkable improvements in computer performance. Computational physics replicates physical phenomena where a large number of elements, such as electrons, ions, people, cars, and money, interact one another by simulation. When electrons move, a current occurs, and when cars are driven slowly, a traffic jam occurs. Computational physics helps us to understand the root causes of those phenomena and provide control over them.
Visual presentation of a condition which you would not normally experience in your daily life, such as extremely low temperatures and extremely high pressures, or a collective phenomenon which happens in a fraction of time or in a small space that would never be detectable by the five senses possessed by humans is made possible by computational physics. Going beyond the supportive roll of bridging theorising and experimentation, we venture into an area that adds a new aspect to contemporary science.

Space journey of science guided by the Einstein equations

Newtonian mechanics is capable of explaining the world where no interrelation exists between matter, space, and time, and is thus inappropriate to explain phenomena in vast areas of the universe. This problem was solved by Einstein's equations. We would never sense it in our daily life, but, strictly speaking, the presence of matter distorts its surrounding space and changes the way that time progresses. Einstein's equations tell us that space, time, and matter are related and influence each other, and they have made it possible to explain why light is curved by gravity or to produce exact calculation on the motion of the planets. The expansion of the universe is also a conclusion derived from the equations.
These equations are very much appropriate to the description of the universe, bringing our scientific enquiry deep into the universe beyond time and space.

Crack the messages from the universe

The universe has been expanding since its birth 13.7 billion years ago. So far, we have gained an understanding of a mere 4% of the constituting matter. The rest, 96% of the universe, is known as dark matter and dark energy. Many researchers observe the universe using a variety of techniques, trying to discover a clue that will unlock the messages arriving from outer space.