Condensed matter physics division

We study theoretically and numerically quantum hydrodynamics in quantum condensed system such as superfluid helium and cold atoms etc.

Research Topics: Experimental study of physical properties in helium and metal materials developed at ultralow temperatures near the absolute zero temperature. Present topics are the vortex, the viscosity, the sound wave, and the NMR of superfluid helium-3 and helium-4. In our laboratory, we study the unknown properties appearing in the macroscopic quantum state of superfluid helium refrigerated at ultralow temperature. In the macroscopic quantum state, all helium atoms condensate in a single state having a wave property; for instance, the phase of the circulation in the flow should be quantized into the integral multiple of 2 pi. As shown in the photo, we have succeeded in making a giant vortex flow in superfluid helium, to study the understanding of superfluid wave properties and the quantization of a superfluid flow.

Main research topics

Our studies of quantum dynamics and resonance phenomena in open quantum systems are aimed at revealing fundamental dynamical principles as well as developing concepts useful from a quantum control perspective. For example, coalescing eigenstates at exceptional points can be used to modify the usual exponential decay process or to control non-Markovian dynamics that may be useful in quantum information processing.

The vast number of electrons in solids correlate with each other through
interactions, resulting in phase transitions such as superconductivity
and magnetism, and the realization of various quantum states such as the Kondo effect and fractional quantum Hall effect. In this laboratory, we are studying fundamental problems of quantum phenomena in such
many-electron systems, using field-theoretical approaches and numerical methods.

Nonlinear physics treats a variety of phenomena which are not represented by linear equations. Nonlinearity is also known to be related to rich phenomena such as complex time series and beautiful patterns. It has flexible enough to treat living things, social phenomena and other subjects that ordinary "physics" does not treat. Theories and numerical models are good tools in research, but real data analysis is also important.

By combining biophysics and optofluidic science, we study the formation process of macroscopic ordered structure from interactions and fluctuations between microscopic biomaterials. In particular, our research will expand from the elucidation of the control principles of various biological functions by “optical condensation” for the creation of novel technologies.

1) Elucidation of the principle for high-throughput “optical condensation” and biological applications.

2) Elucidation of the principle of “light-induced acceleration” of biochemical reactions and biological measurements.

3) Fluid control based on photothermal fluidics and the search for new physical properties.

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Research: We experimentally study the semiconductor physics in which light plays important roles. We are particularly working on the following

1. tracking changes in electronic states of organic LEDs and solar cells during operation by spectroscopy
2. pursuing electron spin properties of operating organic LEDs
3. Magnetic resonance measurement of spin currents

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In our laboratory, we conduct experiments to search for unknown physical properties using atomic gases cooled to near absolute zero (minus 273 degrees Celsius) using laser cooling and other methods. The interaction of cooled atomic gases can be freely controlled using a magnetic field, enabling quantum simulation experiments of various materials. We conduct not only experiments that contribute to the elucidation of a wide range of physical phenomena, such as phase separation of mixed superfluids and simulations of neutron stars, but also precision experiments such as the time variation of fundamental physical constants.

In Molecular Magnetism Laboratory, we synthesize new quantum spin systems using organic radical molecules and transition metal ions, aiming to discover new physical phenomena such as quantum magnetic states and phase transitions through the measurements of various physical properties at low temperatures and in magnetic fields. As shown in the figure, the electron spins of organic radicals are widely distributed throughout the molecule, making it possible to design magnetic lattices through molecular design. We do both the synthesis of new materials and the physical measurements including the development of measurement systems. We clarify quantum magnetic states through macroscopic and microscopic physical property measurements and elucidate the quantization mechanism. We believe that the interplay of magnetism and electricity or elasticity, and the spin thermal conduction will lead to device applications.

In our laboratory, we are studying to elucidate the physical and chemical properties of materials based on the spatial distribution of atoms, molecules, and electrons obtained by X-ray crystal structure analysis. We are mainly conducting X-ray diffraction experiments for X-ray crystal structure analysis using the high-brilliance synchrotron radiation light source of SPring-8. The crystal structure of a material changes depending on temperature, pressure, magnetic field, etc., and is closely related to the properties and functions of the material. We will contribute to the development of materials science by the investigation of the mechanism of physical properties and functions observing in detail the distance between atoms and molecules and the charge distribution.

We aim to contribute to thermoelectric conversion technology by looking at a wide range of research from materials science to thermoelectric conversion engineering from various viewpoints and clarifying the essence of things.