Condensed Matter Experiment Ⅰ

Strongly Correlated Electron Physics

Staff

Visiting Professor : Taichi Terashima Hiroshi Kumigashira Hiroshi Yamamoto

Research

Strongly Correlated Electron Physics Group consists of three guest professors belonging to national and independent research institutes. Research topics of each group are as follows.

Taichi Terashima (National Institute of Materials Science)
URL: http://www.nims.go.jp/nqt/index.html

20-Tesla superconducting magnet with dilution refrigerator.

Our main research areas are electronic structures, superconductivity, and magnetism of highly-correlated materials including iron-pnicitde superconductors, and Ce and U-based heavy fermions. We use high-field magnets installed at the Tsukuba Magnet Laboratory of the National Institute for Materials Science in Tsukuba. We especially focus on performing quantum oscillation measurements. The motion of electrons in magnetic fields is quantized, which results in quantum oscillation of physical properties of metals such as magnetization or resistivity as a function of magnetic field at very low temperatures. From quantum oscillation measurements we can determine the Fermi surface and effective masses of electrons, which are vital information to understand electronic structures of metals. Our main apparatus consists of a 20-Tesla superconducting magnet and dilution refrigerator, in which samples can be cooled down to 0.03 K. We can also apply high pressure of 3 GPa to samples to tune their electronic states.

Hiroshi Kumigashira (KEK-Photon Factory)
URL: http://oxides.kek.jp/index_e.html

Combination of sophisticated oxide growth techniques and advanced analysis techniques using synchrotron radiation.

The goal of our group is to control the novel physical properties appearing at the heterointerface of strongly correlated oxide. For this purpose, we utilize the synchrotron radiation spectroscopic techniques having the elemental selectivity, which enable us to determine the electronic, magnetic, and orbital structures in the nm-scale region at oxide interfaces. For example, the electronic structure at the interface is determined by photoemission spectroscopy (PES) and x-ray absorption spectroscopy (XAS), the magnetic structure by magnetic circular dichroism of XAS, and the orbital structure by linear dicroism of XAS. We aim to design the novel quantum phenomena by the best possible combination of sophisticated oxide growth techniques using laser molecular beam epitaxy and advanced analysis techniques using synchrotron radiation.

Hiroshi Yamamoto (Institute for Molecular Science)
URL: http://yamamoto-tokyo.jp/ims/english/index

Our research focuses on phase transitions of strongly correlated systems induced at an organic field-effect-transistor (FET) interface. Because
the electronic phase of Mott-insulator, one of the typical strongly correlated materials, is very sensitive to its electron density, phase transitions such as insulator-to-metal or insulator-to-superconductor transitions can be controlled by an electric field in FET. Such an electrically switchable phase transition is expected to be utilized for highly efficient circuit in future electronic devices. Recently, we have also succeeded in developing light-induced superconductivity at an organic Mott-insulating interface.


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