Quasi-fractionalization of edge spin in chirality-assisted cluster-based Haldane state on triangular spin tube

Sugimoto, Takanori*; Toyama, Takami

Communications Physics (Internet), 6, p.291_1 - 291_6, 2023/10

https://doi.org/10.1038/s42005-023-01399-3

Higher-dimensional Hofstadter butterfly on the Penrose lattice

Ghadimi, R.*; Sugimoto, Takanori*; Toyama, Takami

Physical Review B, 106(20), p.L201113_1 - L201113_6, 2022/11

https://doi.org/10.1103/PhysRevB.106.L201113

The Role of silicon on solute clustering and embrittlement in highly neutron-irradiated pressurized water reactor surveillance test specimens

Takamizawa, Hisashi; Hata, Kuniki; Nishiyama, Yutaka; Toyama, Takeshi*; Nagai, Yasuyoshi*

Journal of Nuclear Materials, 556, p.153203_1 - 153203_10, 2021/12

https://doi.org/10.1016/j.jnucmat.2021.153203

Solute clusters (SCs) formed in pressurized water reactor surveillance test specimens neutron-irradiated to a fluence of 1 10 n/cm were analyzed via atom probe tomography to understand the effect of silicon on solute clustering and irradiation embrittlement of reactor pressure vessel steels. In high-Cu bearing materials, Cu atoms were aggregated at the center of cluster surrounded by the Ni, Mn, and Si atoms like a core-shell structure. In low-Cu bearing materials, Ni, Mn, and Si atoms formed cluster and these solutes were not comprised core-shell structure in SCs. While the number of Cu atoms in clusters was decreased with decreasing nominal Cu content, the number of Si atoms had clearly increased. The cluster radius () and number density () decreased and increased, respectively, with increasing nominal Si content. The shift in the reference temperature for nil-ductility transition (RT) showed a good correlation with the square root of volume fraction () multiplied by r (). This suggested that the dislocation cutting through the particles mechanism dominates the precipitation hardening responsible for irradiation embrittlement. The negative relation between the nominal Si content and RT indicated that increasing of nominal Si content reduces the degree of embrittlement.

Coexistence of strong and weak Majorana zero modes in an anisotropic XY spin chain with second-neighbor interactions

Wada, Kazuhiro*; Sugimoto, Takanori*; Toyama, Takami

Physical Review B, 104(7), p.075119_1 - 075119_12, 2021/08

https://doi.org/10.1103/PhysRevB.104.075119

Atomistic modeling of hardening in spinodally-decomposed Fe-Cr binary alloys

Suzudo, Tomoaki; Takamizawa, Hisashi; Nishiyama, Yutaka; Caro, A.*; Toyama, Takeshi*; Nagai, Yasuyoshi*

Journal of Nuclear Materials, 540, p.152306_1 - 152306_10, 2020/11

https://doi.org/10.1016/j.jnucmat.2020.152306

Spinodal decomposition in thermally aged Fe-Cr alloys leads to significant hardening, which is the direct cause of the so-called 475C-embrittlement. To illustrate how spinodal decomposition induces hardening by atomistic interactions, we conducted a series of numerical simulations as well as reference experiments. The numerical results indicated that the hardness scales linearly with the short-range order (SRO) parameter, while the experimental result reproduced this relationship within statistical error. Both seemingly suggest that neighboring Cr-Cr atomic pairs essentially cause hardening, because SRO is by definition uniquely dependent on the appearance probability of such pairs. A further numerical investigation supported this notion, as it suggests that the dominant cause of hardening is the pinning effect of dislocations passing over such Cr-Cr pairs.

Dynamical density matrix renormalization group study of spin and charge excitations in the four-leg --

Toyama, Takami; Mori, Michiyasu; Sota, Shigetoshi*

Physical Review B, 97(23), p.235137_1 - 235137_7, 2018/06

AA2018-0171.pdf:1.43MB

https://doi.org/10.1103/PhysRevB.97.235137

Observation of momentum-dependent charge excitations in hole-doped cuprates using resonant inelastic X-ray scattering at the oxygen edge

Ishii, Kenji*; Toyama, Takami*; Asano, Shun*; Sato, Kentaro*; Fujita, Masaki*; Wakimoto, Shuichi; Tsutsui, Kenji*; Sota, Shigetoshi*; Miyawaki, Jun*; Niwa, Hideharu*; et al.

Physical Review B, 96(11), p.115148_1 - 115148_8, 2017/09

AA2017-0402.pdf:0.81MB

https://doi.org/10.1103/PhysRevB.96.115148

Quasi-spin correlations in a frustrated quantum spin ladder

Sugimoto, Takanori*; Mori, Michiyasu; Toyama, Takami*; Maekawa, Sadamichi

Physics Procedia, 75, p.861 - 867, 2015/12

https://doi.org/10.1016/j.phpro.2015.12.111

Lifshitz transition induced by magnetic field in frustrated two-leg spin-ladder systems

Sugimoto, Takanori*; Mori, Michiyasu; Toyama, Takami*; Maekawa, Sadamichi

JPS Conference Proceedings (Internet), 8, p.034005_1 - 034005_6, 2015/09

https://doi.org/10.7566/JPSCP.8.034005

Enhanced charge excitations in electron-doped cuprates by resonant inelastic X-ray scattering

Toyama, Takami*; Tsutsui, Kenji; Mori, Michiyasu; Sota, Shigetoshi*; Yunoki, Seiji*

Physical Review B, 92(1), p.014515_1 - 014515_8, 2015/07

https://doi.org/10.1103/PhysRevB.92.014515

Resonant inelastic X-ray scattering (RIXS) tuned for Cu edge is a possible tool to detect charge excitations in cuprate superconductors. We theoretically investigate the possibility for observing a collective charge excitation by the RIXS. The RIXS process via the intermediate state inevitably makes the spectral weight of charge excitation stronger in electron doping than in hole doping. Electron-hole asymmetry also appears in dynamical charge structure factor, showing a new enhanced small-momentum low-energy mode in electron doping. These facts indicate a possibility of detecting the new charge mode by RIXS in electron-doped systems.