Anomalous vortex dynamics in the spin-triplet superconductor UTe

Tokiwa, Yoshifumi; Sakai, Hironori; Kambe, Shinsaku; Opletal, P.; Yamamoto, Etsuji; Kimata, Motoi*; Awaji, Satoshi*; Sasaki, Takahiko*; Yanase, Yoichi*; Haga, Yoshinori; et al.

Physical Review B, 108(14), p.144502_1 - 144502_5, 2023/10

https://doi.org/10.1103/PhysRevB.108.144502

The vortex dynamics in the spin-triplet superconductor, UTe, are studied by measuring the DC electrical resistivity with currents along the -axis under magnetic fields along the -axis. Surprisingly, we have discovered an island region of low critical current deep inside the superconducting (SC) state, well below the SC upper critical field, attributed to a weakening of vortex pinning. Notably, this region coincides with the recently proposed intermediate-field SC state. We discuss the possibility of nonsingular vortices in the intermediate state, where SC order parameter does not vanish entirely in the vortex cores due to the mixing of multiple SC components.

Ferromagnetic crossover within the ferromagnetic order of UTe

Opletal, P.; Sakai, Hironori; Haga, Yoshinori; Tokiwa, Yoshifumi; Yamamoto, Etsuji; Kambe, Shinsaku; Tokunaga, Yo

Journal of the Physical Society of Japan, 92(3), p.034704_1 - 034704_5, 2023/03

https://doi.org/10.7566/JPSJ.92.034704

We investigate the physical properties of a single crystal of uranium telluride UTe. We have confirmed that UTe crystallizes in the hexagonal structure with three nonequivalent crystallographic uranium sites. The paramagnetic moments are estimated to be approximately 1 per the uranium site, assuming a uniform moment on all the sites. A ferromagnetic phase transition occurs at = 48 K, where the in-plane magnetization increases sharply, whereas the out of-plane component does not increase significantly. With decreasing temperature further below under field-cooling conditions, the out-of-plane component increases rapidly around T= 26 K. In contrast, the in-plane component hardly changes at T. Specific heat measurement indicates no -type anomaly around T, so this is a cross-over suggesting a reorientation of the ordering moments or successive magnetic ordering on the part of the multiple uranium sites.

Effect of uranium deficiency on normal and superconducting properties in unconventional superconductor UTe

Haga, Yoshinori; Opletal, P.; Tokiwa, Yoshifumi; Yamamoto, Etsuji; Tokunaga, Yo; Kambe, Shinsaku; Sakai, Hironori

Journal of Physics; Condensed Matter, 34(17), p.175601_1 - 175601_7, 2022/04

https://doi.org/10.1088/1361-648X/ac5201

Anisotropic physical properties of layered antiferromagnet UPtGa

Matsumoto, Yuji*; Haga, Yoshinori; Yamamoto, Etsuji; Takeuchi, Tetsuya*; Miyake, Atsushi*; Tokunaga, Masashi*

Journal of the Physical Society of Japan, 90(7), p.074707_1 - 074707_6, 2021/07

https://doi.org/10.7566/JPSJ.90.074707

Electronic structure of URuSi in paramagnetic phase; Three-dimensional angle resolved photoelectron spectroscopy study

Fujimori, Shinichi; Takeda, Yukiharu; Yamagami, Hiroshi; Yamamoto, Etsuji; Haga, Yoshinori

Electronic Structure (Internet), 3(2), p.024008_1 - 024008_8, 2021/06

https://doi.org/10.1088/2516-1075/abfd20

The -electron state of the heavy fermion superconductor NpPdAl and the isostructural family

Metoki, Naoto; Aczel, A. A.*; Aoki, Dai*; Chi, S.*; Fernandez-Baca, J. A.*; Griveau, J.-C.*; Hagihara, Masato*; Hong, T.*; Haga, Yoshinori; Ikeuchi, Kazuhiko*; et al.

JPS Conference Proceedings (Internet), 30, p.011123_1 - 011123_6, 2020/03

https://doi.org/10.7566/JPSCP.30.011123

Rare earths (4) and actinides (5) provide variety of interesting states realized with competing interactions between the increasing number of electrons. Since crystal field splitting of many-body electron system is smaller than the bandwidth, (1) high resolution experiments are needed, (2) essentially no clear spectrum with well defined peaks is expected in itinerant Ce and U compounds, and (3) Np and Pu is strictly regulated. Therefore, systematic research on magnetic excitations by neutron scattering experiments of localized compounds and rare earth iso-structural reference is useful. We describe the electron states of heavy electron compounds NpPdAl and actinide and rare earth based iso-structural family.

NMR studies on antiferromagnetic fluctuation in UPt

Aoyama, Taisuke*; Kotegawa, Hisashi*; To, Hideki*; Kimura, Noriaki*; Haga, Yoshinori; Yamamoto, Etsuji; Onuki, Yoshichika*

Physica B; Condensed Matter, 570, p.349 - 351, 2019/10

https://doi.org/10.1016/j.physb.2018.02.031

Evidence for weak spin-orbit interaction experienced by Cooper pairs in the spin-triplet superconductor UPt; Pt-NMR study

Aoyama, Taisuke*; Kotegawa, Hisashi*; Kimura, Noriaki*; Yamamoto, Etsuji; Haga, Yoshinori; Onuki, Yoshichika*; To, Hideki*

Journal of the Physical Society of Japan, 88(6), p.064706_1 - 064706_7, 2019/06

https://doi.org/10.7566/JPSJ.88.064706

Novel critical behavior of magnetization in URhSi; Similarities to the uranium ferromagnetic superconductors UGe and URhGe

Tateiwa, Naoyuki; Haga, Yoshinori; Yamamoto, Etsuji

Physical Review B, 99(9), p.094417_1 - 094417_12, 2019/03

https://doi.org/10.1103/PhysRevB.99.094417

We study the critical behavior of dc magnetization in the uranium ferromagnet URhSi around the ferromagnetic phase transition at 10 K. The critical exponent for the spontaneous magnetization below , for the magnetic susceptibility, and for the magnetic isotherm at have been determined as = 0.300 0.002, = 1.00 0.02, and = 4.32 0.04 by the scaling analysis and the critical isotherm analysis. Magnetization has strong uniaxial magnetic anisotropy in the ferromagnetic state of URhSi. However, the universality class of the critical phenomenon does not belong to the 3D Ising system ( = 0.325, = 1.241, and = 4.82). The obtained exponents in URhSi are similar to those in uranium ferromagnetic superconductors UGe and URhGe. We discuss the static and dynamical magnetic properties of URhSi in comparison with those in UGe, URhGe and UCoGe.

Strong correlation between ferromagnetic superconductivity and pressure-enhanced ferromagnetic fluctuations in UGe

Tateiwa, Naoyuki; Haga, Yoshinori; Yamamoto, Etsuji

Physical Review Letters, 121(23), p.237001_1 - 237001_6, 2018/12

https://doi.org/10.1103/PhysRevLett.121.237001

We have measured magnetization at high pressure in the uranium ferromagnetic superconductor UGe and analyzed the magnetic data using Takahashi's spin fluctuation theory. There is a peak in the pressure dependence of the width of the spin fluctuation spectrum in the energy space at , the phase boundary of FM1 and FM2 where the superconducting transition temperature is highest. This suggests a clear correlation between the superconductivity and pressure-enhanced magnetic fluctuations developed at . The pressure effect on , where is the Curie temperature, suggests that the less itinerant ferromagnetic state FM2 is changed to a more itinerant one FM1 across . Peculiar features in relations between and in uranium ferromagnetic superconductors UGe, URhGe and UCoGe are discussed in comparison with those in high- cuprate and heavy fermion superconductors.