Polarization dependence of soft X-ray absorption spectroscopy on the heavy fermion superconductor CeNiGe

Fujiwara, Hidenori*; Nakatani, Yasuhiro*; Aratani, Hidekazu*; Kanai-Nakata, Yuina*; Yamagami, Kohei*; Hamamoto, Satoru*; Kiss, Takayuki*; Sekiyama, Akira*; Tanaka, Arata*; Ebihara, Takao*; et al.

New Physics; Sae Mulli, 73(12), p.1062 - 1066, 2023/12

https://doi.org/10.3938/NPSM.73.1062

Nested antiferromagnetic spin fluctuations and non-Fermi-liquid behavior in electron-doped CeCoNiIn

Sakai, Hironori; Tokunaga, Yo; Kambe, Shinsaku; Zhu, J.-X.*; Ronning, F.*; Thompson, J. D.*; Kotegawa, Hisashi*; To, Hideki*; Suzuki, Kohei*; Oshima, Yoshiki*; et al.

Physical Review B, 106(23), p.235152_1 - 235152_8, 2022/12

https://doi.org/10.1103/PhysRevB.106.235152

We investigate the electronic state of Ni-substituted CeCoNiIn by nuclear quadrupole and magnetic resonance (NQR/NMR) techniques. The heavy fermion superconductivity below K for is suppressed by Ni substitutions, and reaches zero for . The In NQR spectra for and 0.25 can be explained by simulating the electrical field gradient that is calculated for a virtual supercell with density functional theory. The spin-lattice relaxation rate indicates that Ni substitution weakens antiferromagnetic correlations that are not localized near the substituent but instead are uniform in space. The temperature () dependence of for shows a maximum around K and decreases toward almost zero when temperature is further reduced as if a gap might be opening in the magnetic excitation spectrum; however, the magnetic specific heat and the static magnetic susceptibility evolve smoothly through with a dependence. The peculiar T dependence of and non-Fermi-liquid specific heat and susceptibility can be interpreted in a unified way by assuming nested antiferromagnetic spin fluctuations in a quasi-two-dimensional electronic system.

Nanoscale heterogeneity induced by nonmagnetic Zn dopants in the quantum critical metal CeCoIn; In NQR/NMR and Co NMR study

Sakai, Hironori; Tokunaga, Yo; Kambe, Shinsaku; Zhu, J.-X.*; Ronning, F.*; Thompson, J. D.*; Ramakrishna, S. K.*; Reyes, A. P.*; Suzuki, Kohei*; Oshima, Yoshiki*; et al.

Physical Review B, 104(8), p.085106_1 - 085106_12, 2021/08

https://doi.org/10.1103/PhysRevB.104.085106

Antiferromagnetism in a prototypical quantum critical metal CeCoIn is known to be induced by slight substitutions of non-magnetic Zn atoms for In. In nominally 7% Zn substituted CeCoIn, an antiferromagnetic (AFM) state coexists with heavy fermion superconductivity. Heterogeneity of the electronic states is investigated in Zn doped CeCoIn by means of nuclear quadrupole and magnetic resonances (NQR and NMR). Site-dependent NQR relaxation rates indicate that the AFM state is locally nucleated around Zn substituents in the matrix of a heavy fermion state, and percolates through the bulk at the AFM transition temperature . At lower temperatures, an anisotropic superconducting (SC) gap below the SC transition temperature , and the SC state permeates through the AFM regions via a SC proximity effect. Applying an external magnetic field induces a spin-flop transition near 5 T, reducing the volume of the AFM regions. Consequently, a short ranged inhomogeneous AFM state survives and coexists with a paramagnetic Fermi liquid state at high fields.

Universal scaling behavior under pressure in the heavy-fermion antiferromagnet CeRhSi; Si NMR study

Sakai, Hironori; Matsumoto, Yuji*; Haga, Yoshinori; Tokunaga, Yo; Kambe, Shinsaku

Physical Review B, 103(8), p.085114_1 - 085114_8, 2021/02

https://doi.org/10.1103/PhysRevB.103.085114

The microscopic origin of a magnetic phase diagram under pressure in a heavy fermion antiferromagnet CeRhSi was investigated using the Si nuclear magnetic resonance (NMR) technique. We investigated the temperature and pressure dependencies of -independent local fluctuations caused by the single-site Kondo effect. A universal scaling behavior observed on the energy scale of the local fluctuations in an entire pressure region demonstrates that a characteristic energy scale of Kondo interactions monotonically increases by applying pressure without a critical anomaly around the quantum critical pressure of antiferromagnetism. Our NMR result agrees with the Doniach picture of the heavy-fermion phase diagram, where the progressive delocalization of the -electrons occurs across , accompanied by the development of antiferromagnetic correlations among the -electrons.

High-field phase diagram of the heavy-fermion metal CeIn; Pulsed-field NMR study on single crystals up to 56 T

Tokunaga, Yo; Orlova, A.*; Bruyant, N.*; Aoki, Dai*; Mayaffre, H.*; Krmer, S.*; Julien, M.-H.*; Berthier, C.*; Horvati, M.*; Higa, Nonoka; et al.

Physical Review B, 99(8), p.085142_1 - 085142_5, 2019/02

https://doi.org/10.1103/PhysRevB.99.085142

The heavy-fermion antiferromagnet CeIn exhibits a field-induced anomaly associated with Fermi surface reconstruction at 45 T, well below the antiferromagnetic (AFM) critical field that exceeds 60 T. In order to explore the origin of this anomaly, we have measured In NMR spectra in pulsed magnetic fields up to 56 T using high-quality single crystals. To within experimental resolution, we do not detect any change in the NMR spectra that could suggest a modification in either the character of the hyperfine field or the electric field gradient at In sites through . This strongly suggests that the 45 T anomaly cannot be simply ascribed to a field-induced change in the magnetic structure of the AFM state.

Evidence for momentum-dependent heavy fermionic electronic structures; Soft X-ray ARPES for the superconductor CeNiGe in the normal state

Nakatani, Yasuhiro*; Aratani, Hidekazu*; Fujiwara, Hidenori*; Mori, Takeo*; Tsuruta, Atsushi*; Tachibana, Shoichi*; Yamaguchi, Takashi*; Kiss, Takayuki*; Yamasaki, Atsushi*; Yasui, Akira*; et al.

Physical Review B, 97(11), p.115160_1 - 115160_7, 2018/03

AA2018-0003.pdf:1.65MB

https://doi.org/10.1103/PhysRevB.97.115160

Colossal thermomagnetic response in the exotic superconductor URuSi

Yamashita, Takuya*; Shimoyama, Yusuke*; Haga, Yoshinori; Matsuda, Tatsuma*; Yamamoto, Etsuji; Onuki, Yoshichika; Sumiyoshi, Hiroaki*; Fujimoto, Satoshi*; Levchenko, A.*; Shibauchi, Takasada*; et al.

Nature Physics, 11(1), p.17 - 20, 2015/01

https://doi.org/10.1038/nphys3170

Magnetism and superconductivity in CePtSi probed by muon spin relaxation

Higemoto, Wataru; Haga, Yoshinori; Matsuda, Tatsuma; Onuki, Yoshichika; Koda, Akihiro*; Saha, S. R.*; Oishi, Kazuki; Kadono, Ryosuke*

Journal of the Physical Society of Japan, 75(Suppl.), p.180 - 182, 2006/08

We report on the Magnetism, magnetic penetration depth and the Knight shift in polycrystalline sample of CePtSi by means of muon spin rotation and relaxation method. The appearance of the internal field under the zero magnetic field in whole volume of the specimen, was observed, which indicating clear evidence of antiferromagnetism. The muon Knight shift was measured down to 20mK at 17kOe. Three different frequencies are seen in the muon spin rotation spectra, which depend on the temperature. The symmetry of the superconducting Cooper pair will be discussed.

Direct observation of a quasiparticle band in CeIrIn; An Angle-resolved photoemission spectroscopy study

Fujimori, Shinichi; Fujimori, Atsushi; Shimada, Kenya*; Narimura, Takamasa*; Kobayashi, Kenichi*; Namatame, Hirofumi*; Taniguchi, Masaki*; Harima, Hisatomo*; Shishido, Hiroaki*; Ikeda, Shugo; et al.

Physical Review B, 73(22), p.224517_1 - 224517_5, 2006/06

https://doi.org/10.1103/PhysRevB.73.224517

We have performed a high-resolution angle resolved Ce 4-4 resonant photoemission experiment on the heavy fermion superconductor CeIrIn. We have observed a quasi-particle band which has a energy disepersion of 30 meV in the Ce 4 on-resonance spectra. The result suggests that although the Ce 4 spectra are dominated by the localized/correlated character being dominant, the small itinerant component is responsible for the superconductivity in this compound.

Soft X-ray synchrotron radiation photoemission study on uranium compounds

Fujimori, Shinichi; Terai, Kota; Takeda, Yukiharu; Okane, Tetsuo; Saito, Yuji; Muramatsu, Yasuji; Fujimori, Atsushi; Yamagami, Hiroshi*; Ikeda, Shugo; Matsuda, Tatsuma; et al.

Physica B; Condensed Matter, 378-380, p.995 - 996, 2006/05

https://doi.org/10.1016/j.physb.2006.01.506

Recently, photoemission experiments in soft X-ray region have attracted much attention due to their high sensitivities for bulk electronic structures of strongly correlated electron system. We have carried out the high-resolution photoemission experiments on some uranium compounds using soft X-ray synchrotron radiation from SPring-8 to understand their electronic structures. Bulk- and U 5-sensitive band structure and Fermi surface were obtained for itinerant U 5 compounds UFeGa and USb, and they are compared with the results of the band structure calculations treating U 5 states as being itinerant. In addition, we show the results of photoemission study on some heavy fermion compounds such as UPdAl and UNiAl. The temperature dependences of the U 5 electronic structure of UPdAl will be also reported.