Pairing interaction in superconducting UCoGe tunable by magnetic field

The mechanism of unconventional superconductivity, such as high-temperature-cuprate, Fe-based, and heavy-fermion superconductors, has been studied as a central issue in condensed-matter physics. Spin fluctuations, instead of phonons, are considered to be responsible for the formation of Cooper pairs, and many efforts have been made to confirm this mechanism experimentally. Although a qualitative consensus seems to […]

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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 pressure and peaks at ∼ […]

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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 has been paid to the […]

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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 and the decrease in Kb was almost […]

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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, the phenomenon characterized by the […]

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Magnetic-Field Dependence of Novel Gap Behavior Related to the Quantum-Size Effect

195Pt-NMR measurements of Pt nanoparticles with a mean diameter of 4.0 nm were performed in a high magnetic field of approximately μ0H=23.3 T to investigate the low-temperature electronic state of the nanoparticles. The characteristic temperature T∗, below which the nuclear spin-lattice relaxation rate 1/T1 deviates from the relaxation rate of the bulk, shows a magnetic-field dependence. This dependence supports the […]

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Long magnetic penetration depth observed in Sr3−xSnO

Antiperovskite oxide superconductor Sr3−xSnO was measured by a method called muon spin rotation (μSR). It became clear that the magnetic field penetration depth is abnormally long. Sr3−xSnO is a superconductor discovered in our laboratory in 2016. It is the first superconductor in the antiperovskite oxide, and the possibility of topological superconductivity has been theoretically proposed. […]

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“Diamagnetic” signals can appear due to localised heating

Magnetic differential measurements In order to perform magnetisation measurements, it is usually necessary to put a sample onto a sample holder. If the holder magnetization is exactly zero, it is straightforward to extract the sample magnetisation. However, it is practically impossible to bring the holder magnetisation completely to zero. Thus, it is common to use […]

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Discovery of superconductivity in CaSb2

In CaSb2 , the calcium and antimony atoms are arranged in a special arrangement called “non-conformal”. Since atoms are arranged periodically in a crystal, if one atom moves in parallel so that it overlaps with the next atom, other atoms also overlap with the next atom, resulting in the same structure as the original. I will. In addition to […]

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