Hiroki Matsumura

@article{H.Matsumura_PRB2_2025,

title = {𝑏-axis and 𝑐-axis Knight shift measurements in the superconducting state on ultraclean UTe2 with 𝑇𝑐=2.1 K},

author = {H Matsumura and Y Takahashi and K Kinjo and S Kitagawa and K Ishida and Y Tokunaga and H Sakai and S Kambe and A Nakamura and Y Shimizu and Y Homma and D Li and F Honda and A Miyake and D Aoki},

doi = {10.1103/PhysRevB.111.174526},

year  = {2025},

date = {2025-05-23},

journal = {Physical Review B},

volume = {111},

pages = {174526},

abstract = {Knight shifts along the 𝑏 and 𝑐 axes (𝐾𝑏 and 𝐾𝑐) at two crystallographically distinct Te sites were measured down to 70 mK using  125Te nuclear magnetic resonance on an ultraclean UTe2 single crystal with a superconducting (SC) transition temperature 𝑇𝑐=2.1 K. This was carried out to determine the 𝒅-vector components, which are the order parameter in the spin-triplet pairing. Although the decrease in 𝐾𝑏 and 𝐾𝑐 is comparable to the theoretical estimation of the SC diamagnetic shielding effect, it is confirmed, by taking the difference between two Knight shifts at the distinct Te sites, that the spin susceptibility along the 𝑏 and 𝑐 axes decreases in the SC state. Taking into account the large decrease in 𝐾𝑎 in the SC state, we conclude that the 𝒅 vector has components along all three crystal axes.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{H.Matsumura_PRB_2025-1,

title = {Intrinsic low-temperature magnetic properties on ultraclean UTe2 with Tc = 2.1 K revealed by 125Te NMR},

author = {H Matsumura and S Kitagawa and S Ogata and R Matsubayashi and H Fujibayashi and K Kinjo and K Ishida and Y Tokunaga and H Sakai and S Kambe and A Nakamura and Y Shimizu and Y Homma and D Li and F Honda and A Miyake and D Aoki},

url = {https://doi.org/10.1103/PhysRevB.111.094507

https://arxiv.org/abs/2503.09109},

doi = {10.1103/PhysRevB.111.094507},

year  = {2025},

date = {2025-03-10},

urldate = {2025-03-10},

journal = {Physical Review B},

volume = {111},

pages = {094507},

abstract = {To investigate the intrinsic magnetic properties of UTe2, we performed  125Te-NMR measurements on the ultraclean single-crystalline UTe2 with superconducting transition temperature 𝑇c=2.1 K and compared the results with those of the 𝑇c=1.6 K sample. The broadening of the linewidth of the NMR spectrum in the 𝑎-axis magnetic field and the low-temperature magnetic fluctuations observed in the 1.6 K sample are suppressed in the ultraclean sample, indicating that such magnetic properties originate from a tiny amount of U deficiency. The present results suggest that the magnetic properties in UTe2 are sensitive to the U deficiency. We also observed a peculiar angular dependence of the NMR quantities due to large magnetic anisotropy with the 𝑎 axis as the magnetic easy axis.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{S.Kitagawa_JPSJ_2024,

title = {Clear Reduction in Spin Susceptibility and Superconducting Spin Rotation for H || a in the Early-Stage Sample of Spin-Triplet Superconductor UTe2},

author = {S Kitagawa and K Nakanishi and H Matsumura and Y Takahashi and K Ishida and Y Tokunaga and H Sakai and S Kambe and A Nakamura and Y Shimizu and D Li and F Honda and A Miyake and D Aoki},

url = {https://doi.org/10.7566/JPSJ.93.123701

https://arxiv.org/abs/2411.02698},

doi = {10.7566/JPSJ.93.123701},

year  = {2024},

date = {2024-11-01},

urldate = {2024-11-01},

journal = {Journal of the Physical Society of Japan},

volume = {93},

pages = {123701},

abstract = {We report the re-measurement of the a-axis spin susceptibility component in an early-stage sample of the spin-triplet superconductor UTe2 with the transition temperature of TSC = 1.6 K. Using Knight-shift measurements along the b axis and at a 10-degree tilt from the b axis towards the a axis, we accurately determined the a-axis component without directly measuring the a-axis Knight shift. Our results reveal a decrease of approximately 3% in the a-axis spin susceptibility in the superconducting state under a-axis magnetic field μ0Ha ∼ 0.1 T, indicating that the spin susceptibility decreases similarly in both early-stage and ultraclean samples with TSC = 2.1 K. The previously reported absence of the reduction in Knight shift is attributed to the missing of signal from the superconducting region and to the detection of residual signals from the non-superconducting region instead. We also found that the decrease in the a-axis spin susceptibility is immediately suppressed with increasing the a-axis magnetic field and is estimated to be completely suppressed at around 1.5 T due to superconducting spin rotation.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Superconducting spin reorientation in spin-triplet multiple superconducting phases of UTe2},

author = {K Kinjo and H Fujibayashi and H Matsumura and F Hori and S Kitagawa and K Ishida and Y Tokunaga and H Sakai and S Kambe and A Nakamura and Y Shimizu and Y Homma and D Li and F Honda and D Aoki},

url = {https://arxiv.org/abs/2307.15784},

doi = {10.1126/sciadv.adg2736},

year  = {2023},

date = {2023-07-28},

urldate = {2023-07-28},

journal = {Science Advances},

volume = {9},

pages = {adg2736},

abstract = {Superconducting (SC) state has spin and orbital degrees of freedom, and spin-triplet superconductivity shows multiple SC phases because of the presence of these degrees of freedom. However, the observation of spin-direction rotation occurring inside the SC state (SC spin rotation) has hardly been reported. Uranium ditelluride, a recently found topological superconductor, exhibits various SC phases under pressure: SC state at ambient pressure (SC1), high-temperature SC state above 0.5 gigapascal (SC2), and low-temperature SC state above 0.5 gigapascal (SC3). We performed nuclear magnetic resonance (NMR) and ac susceptibility measurements on a single-crystal uranium ditelluride. The b axis spin susceptibility remains unchanged in SC2, unlike in SC1, and decreases below the SC2-SC3 transition with spin modulation. These unique properties in SC3 arise from the coexistence of two SC order parameters. Our NMR results confirm spin-triplet superconductivity with SC spin parallel to b axis in SC2 and unveil the remaining of spin degrees of freedom in SC uranium ditelluride.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{H.Matsumura_JPSJ_2023,

title = {Large Reduction in the a-axis Knight Shift on UTe2 with Tc = 2.1 K},

author = {H Matsumura and H Fujibayashi and K Kinjo and S Kitagawa and K Ishida and Y Tokunaga and H Sakai and S Kambe and A Nakamura and Y Shimizu and Y Homma and D Li and F Honda and D Aoki },

url = {https://arxiv.org/abs/2305.01200},

doi = {10.7566/JPSJ.92.063701},

year  = {2023},

date = {2023-05-16},

urldate = {2023-05-16},

journal = {Journal of the Physical Society of Japan},

volume = {92},

pages = {063701},

abstract = {Spin susceptibility in the superconducting (SC) state was measured in the higher-quality sample of uranium-based superconductor UTe2 by using Knight-shift measurements for a magnetic field H along all three crystalline axes. In the higher-quality sample, the SC transition temperature Tc is about 2.1 K, and the residual electronic term in the specific heat is almost zero. The NMR linewidth becomes narrower and is almost half of that in the previous sample with Tc ∼ 1.6 K when H || a and c. Although the Knight-shift behavior was not so different from the previous results for H || b, and c, a large reduction in Knight shift along the a axis was observed, in contrast with the previous a-axis Knight shift result. We discuss the origin of the difference between the previous and present results, and the possible SC state derived from the present results.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}