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Peak in the superconducting transition temperature of the nonmagnetic topological line-nodal material CaSb2 under pressure

Peak in the superconducting transition temperature of the nonmagnetic topological line-nodal material CaSb2 under pressure

Investigating the pressure dependence of the superconducting (SC) transition temperature Tc is crucial for understanding the SC mechanism. Herein, we report on the pressure dependence of Tc in the nonmagnetic topological line-nodal material CaSb2, based on measurements of electric resistance and alternating current magnetic susceptibility. Tc initially increases with increasing...
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Observation of s-wave superconductivity in CaSb2

Observation of s-wave superconductivity in CaSb2

CaSb2 has a crystal structure with a special arrangement called “non-symmorphic’’. Due to this structure, it is expected that the bulk electronic energy bands have four-fold degeneracy along a line in the momentum space, which is called Dirac line node. In 2020, we discovered that CaSb2 exhibits superconductivity. Much attention...
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Happy graduation!

Happy graduation!

The graduation ceremony and degree conferral ceremony were held on March 24, 2021! Congratulations to D3/M2/B4 students!
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Anisotropic response of spin susceptibility in the superconducting state of UTe2 probed  with 125Te−NMR measurement

Anisotropic response of spin susceptibility in the superconducting state of UTe2 probed with 125Te−NMR measurement

To investigate spin susceptibility in a superconducting (SC) state, we measured the 125Te-nuclear magnetic resonance (NMR) Knight shifts at magnetic fields (H) up to 6.5 T along the b and c axes of single-crystal UTe2, a promising candidate for a spin-triplet superconductor. In the SC state, the Knight shifts along the b and c axes (Kb and Kc, respectively) decreased slightly...
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The alignment pattern of nematic superconductivity has been successfully controlled

The alignment pattern of nematic superconductivity has been successfully controlled

In consumer liquid-crystal displays, "nematic" liquid-crystals, in which bar-shaped molecules align along a certain direction, are utilized. Configuration of this molecular alignment can be controlled by an applied voltage, to change the light transparency of each pixel. Recently, "nematic superconductivity", which is analogous to nematic liquid-crystals, has been discovered. Superconductivity,...
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We are a research group in experimental physics at Kyoto University led by Profs. Yoshi Maeno and Kenji Ishida. Our research focuses on various phenomena in strongly correlated materials where strong electron–electron interactions lead to emerging physical properties. These phenomena manifest themselves at temperatures much lower than the ambient one, conditions in which materials are dominated by quantum physics and statistical mechanics. Our main interest involves phenomena such as superconductivity, strong magnetism, and spin ordering effects.

Our group is based on the synergy of two experimental research subgroups: the materials synthesis and characterisation lab led by Prof. Maeno, and the NMR group led by Prof. Ishida. Seminars, scientific discussions, and laboratory activities are conducted jointly by the two groups.

1. Topological superconductors such as Sr2RuO4

Sr2RuO4 is one of the most actively studied superconductors in our laboratory. Our aim is to elucidate the long-standing mystery of its superconducting state by high-purity single crystal growth and precise measurements of electronic transport and magnetism.

2. Material synthesis

New materials are a crucial aspect to discover novel physical phenomena.
In our laboratory, we have succeeded in the synthesis of a large number of materials by the floating zone and flux methods. Notable materials grown in our lab include the superconductor Ag5Pb2O6, the quasi-two-dimensional conductor PdCoO2, the superconductor with broken inversion symmetry CaIrSi3, the new superconductor La3Pt4 and the inverse perovskite oxide superconductor Sr3-xSnO.

3. Microdevices by focused ion beam

We use micro fabrication to reveal new quantum phenomena and study novel material properties.

We also perform studies on small devices, where we can define the material geometry and accurately control the distribution of temperature.

4. Nematic superconductivity

Discovery of nematic superconductivity in CuxBi2Se3, a state in which the superconducting Cooper pairs have a spontaneously broken rotational symmetry.

5. Metal-insulator transitions

We use thermal imaging with materials such as Ca2RuO4 to identify the formation of metallic regions (darker) in a matrix of insulating phase (brighter). This technique allows us to study the formation of metallic regions as a function of current drive.

6. Nuclear magnetic resonance (NMR)

NMR is a powerful measurement tool that allows us to measure electronic and magnetic states on the microscopic scale by using nuclear spins. With this technique, we study the electronic states of a wide range of materials ranging from superconductors to magnetic materials.

7. Uranium-based ferromagnetic superconductivity

For a long time, ferromagnetism and superconductivity were considered to be incompatible. The 5f electrons of uranium compounds, instead, have the special characteristic of being responsible at the same time for both ferromagnetism and superconductivity, two states that are considered to coexist.

We reported several experimental results showing the realisation of a spin triplet state due to ferromagnetic fluctuations in UCoGe.

8. Magnetism and quantum critical phenomena

Several interesting magnetic and superconducting states appear near the quantum critical point of materials. Our research aims to investigate the physical properties near quantum critical points aided by pressure and strong electric and magnetic fields.

9. Quantum size effect in nanoparticles

Nanoparticles can be expected to show unique properties, such as magnetism, metal–insulator transitions, that are due to the discrete nature of the quantum energy levels, which are different from bulk materials. We study quantum size effects in materials such as Pt nanoparticles with NMR measurements.