Article
Multidisciplinary Sciences
Hiroyuki Yamase, Yoshiharu Sakurai, Masaki Fujita, Shuichi Wakimoto, Kazuyoshi Yamada
Summary: Compton scattering provides valuable information about the Fermi surface, revealing that in La2-xSrxCuO4 samples the Fermi surface in the CuO2 plane is deformed due to underlying nematicity, but the bulk Fermi surfaces recover fourfold symmetry.
NATURE COMMUNICATIONS
(2021)
Article
Materials Science, Multidisciplinary
Guido Homann, Jayson G. Cosme, Junichi Okamoto, Ludwig Mathey
Summary: We propose a mechanism for enhancing interlayer transport in cuprate superconductors by optically driving plasmonic excitations along the c axis. The induced collective oscillation of the Higgs field leads to a parametric enhancement of the superconducting response, with potential for more than 50% improvement. Our analytical predictions are supported by simulations of a particle-hole symmetric U(1) lattice gauge theory.
Review
Physics, Multidisciplinary
Mi Jiang
Summary: The recent discovery of superconductivity in doped rare-earth infinite-layer nickelates RNiO2 has sparked extensive research due to its similarities and differences with cuprate superconductors. By investigating the Ni/Cu-3d multiplet structure, researchers have provided insights into the hole-doped spin states in both cuprate and nickelate superconductors, laying a foundation for further exploration in this new family of unconventional superconductors.
Article
Physics, Applied
B. S. Tewari, M. Ahlawat, A. Dhyani, Ajay
Summary: This study investigates the isotope effect in bilayer cuprate superconductors using the BCS-effective Hamiltonian, introducing a pseudo-gap order parameter to examine the momentum dependence of the d-wave superconducting order parameter. The results show that the isotope effect increases with interlayer coupling and decreases with transition temperature, while the presence of a pseudo-gap parameter enhances the isotope effect in the quasi-particle spectrum.
PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS
(2021)
Article
Chemistry, Multidisciplinary
Martin M. Botana, Manuel V. Ramallo
Summary: This study investigates the critical fluctuations near the resistive transition in very thin films of high-temperature cuprate superconductors. The fluctuation spectrum of a Gaussian-Ginzburg-Landau model is solved, considering two alternating Josephson interlayer interaction strengths, to obtain the paraconductivity above the transition. These calculations are then extended to temperatures below the transition using expressions for the Ginzburg number and Kosterlitz-Thouless-like critical region. The results provide a plausible scenario for the critical regime in YBa2Cu3O7-delta few-bilayers systems.
Article
Physics, Condensed Matter
Mehmet Gunay
Summary: In this study, we investigate a system consisting of two atomic species in mixed dimensions. It has been found that the transition from p-wave to s-wave occurs as the ratio of the layer separation and the scattering length decreases. At the critical point of inter-layer pairing, a new force emerges.
JOURNAL OF PHYSICS-CONDENSED MATTER
(2022)
Article
Automation & Control Systems
Jize Xue, Yongqiang Zhao, Yuanyang Bu, Jonathan Cheung-Wai Chan, Seong G. Kong
Summary: This paper proposes a parametric tensor sparsity measure model based on Laplacian scale mixture (LSM) modeling, which can encode the sparsity for a general tensor. By transforming the tensor sparsity into factor sparsity using three-layer transform (TLT) and expressing local similarity within the mode using factor sparsity in the gradient domain, the proposed method can depict hierarchical structure underlying the data. LSM and transform learning scheme further refine the sparsity and depict deeper layer structured sparsity. The experimental results demonstrate the superiority of the proposed method for tensor completion.
IEEE TRANSACTIONS ON CYBERNETICS
(2022)
Article
Chemistry, Multidisciplinary
Ziqian Wang, Meng Gao, Tonghua Yu, Siyuan Zhou, Mingquan Xu, Motoaki Hirayama, Ryotaro Arita, Yuki Shiomi, Wu Zhou, Naoki Ogawa
Summary: Stacking order plays a significant role in the properties of van der Waals layered magnets, and recent studies suggest possible different stackings in few-layer crystals. This study combines atomic-scale electron microscopy and theoretical calculations to show that while the bulk stacking persists in bilayers of MnPS3, the local rippling effect lifts the monoclinic symmetry of the few layers. This finding reveals the impact of rippling on the microscopic symmetry of two-dimensional materials and suggests the possibility of approaching the two-dimensional Neel antiferromagnetic honeycomb lattice in MnPS3 without reaching monolayer thickness.
Article
Multidisciplinary Sciences
Xianzhe Chen, Tomoya Higo, Katsuhiro Tanaka, Takuya Nomoto, Hanshen Tsai, Hiroshi Idzuchi, Masanobu Shiga, Shoya Sakamoto, Ryoya Ando, Hidetoshi Kosaki, Takumi Matsuo, Daisuke Nishio-Hamane, Ryotaro Arita, Shinji Miwa, Satoru Nakatsuji
Summary: The tunnelling magnetoresistance (TMR) in magnetic tunnel junctions (MTJs) is usually studied in ferromagnetic materials, but this study reports the observation of TMR in an all-antiferromagnetic tunnel junction. A TMR ratio of about 2% was measured at room temperature, which is attributed to the configuration of cluster magnetic octupoles in the chiral antiferromagnetic state. Sign and direction of anisotropic longitudinal spin-polarized current in the antiferromagnet can be controlled by octupole direction. Theoretical analysis suggests that the chiral antiferromagnetic MTJ can produce a substantially large TMR ratio due to the time-reversal, symmetry-breaking polarization characteristic of cluster magnetic octupoles.
Article
Multidisciplinary Sciences
Yuto Watanabe, Hiroto Arima, Hidetomo Usui, Yoshikazu Mizuguchi
Summary: The structural, electronic, and superconducting properties of Co1-xNixZr2 were investigated to achieve systematic control of c-axis negative thermal expansion (NTE) and switching from NTE to positive thermal expansion (PTE) by Ni substitution. C-axis NTE was observed at x <= 0.3, and the thermal expansion constant approached zero with increasing x. C-axis thermal expansion close to zero thermal expansion (ZTE) was observed at x = 0.4-0.6, and PTE appeared for x >= 0.7. Analysis of the c/a ratio revealed a possible collapsed transition in the tetragonal lattice at around x = 0.6-0.8, which could be the cause of the suppression of superconductivity and the switching from NTE to PTE in Ni-rich Co1-xNixZr2.
SCIENTIFIC REPORTS
(2023)
Article
Physics, Applied
Takuya Nomoto, Ryotaro Arita
Summary: In recent years, the skyrmion lattice phase with a short lattice constant has been studied for its high skyrmion density and potential applications in high-density storage memory and the observation of novel phenomena like the quantized topological Hall effect. This Perspective focuses on the first-principles evaluations of the formation mechanism and potential skyrmion materials, with a specific focus on the prototype systems GdT2X2 and EuT2X2. The results show that the Hubbard U and Hund's coupling play crucial roles in stabilizing a skyrmion lattice state and that certain materials, such as GdRu2X2 and GdOs2X2, show promise as skyrmion host materials.
JOURNAL OF APPLIED PHYSICS
(2023)
Article
Engineering, Electrical & Electronic
Naoto Nakamura, Yosuke Goto, Yuki Nakahira, Akira Miura, Chikako Moriyoshi, Chul-Ho Lee, Hidetomo Usui, Yoshikazu Mizuguchi
Summary: We demonstrate the thermoelectric transport properties of the Zintl arsenide EuCuAs. The crystal structure of EuCuAs consists of a covalently-bonded honeycomb-type CuAs network sandwiched by nearly divalent Eu ions. Undoped EuCuAs exhibits a relatively high power factor but a limited dimensionless figure-of-merit due to high lattice thermal conductivity. First-principles calculations predict that heavy hole-doped EuCuAs can exhibit axis-dependent conduction polarity, enabling the construction of transverse thermoelectric devices.
JOURNAL OF ELECTRONIC MATERIALS
(2023)
Article
Physics, Condensed Matter
Sharareh Sayyad, Motoharu Kitatani, Abolhassan Vaezi, Hideo Aoki
Summary: We investigate the effects of nematicity, superconductivity, and non-Fermi liquid behavior on partially flat-band (PFB) models on the triangular lattice. Our main finding is that nematicity, driven by many-body effects, enhances the superconducting transition temperature in a systematic manner on the T (c) dome. The breaking of the sixfold symmetry leads to a stronger pairing interaction and more compact pairs in real space, accompanied by a non-Fermi character of electrons in the PFBs with many-body interactions.
JOURNAL OF PHYSICS-CONDENSED MATTER
(2023)
Article
Physics, Multidisciplinary
H. Takagi, R. Takagi, S. Minami, T. Nomoto, K. Ohishi, M. -t. Suzuki, Y. Yanagi, M. Hirayama, N. D. Khanh, K. Karube, H. Saito, D. Hashizume, R. Kiyanagi, Y. Tokura, R. Arita, T. Nakajima, S. Seki
Summary: The spontaneous topological Hall effect in triangular lattice compounds CoTa3S6 and CoNb3S6 is experimentally demonstrated, combining non-coplanar antiferromagnetic order with finite scalar spin chirality in the absence of a magnetic field. These compounds exhibit unconventionally large spontaneous Hall effects despite their small net magnetization, and the mechanism behind this phenomena is explained by the topological Hall effect associated with scalar spin chirality. The results suggest that the scalar spin chirality mechanism offers a promising route for the realization of a giant spontaneous Hall response in compensated antiferromagnets.
Article
Nanoscience & Nanotechnology
Motoharu Kitatani, Yusuke Nomura, Motoaki Hirayama, Ryotaro Arita
Summary: Motivated by recent theoretical materials design, we calculate the phase diagram of RbCa2NiO3 and A(2)NiO(2)Br(2) using the dynamical vertex approximation. We find that these nickelates exhibit similar phase features as cuprates, where superconductivity emerges from hole-doped antiferromagnetic Mott insulators with a dome-like superconducting transition temperature. This highlights the crucial role of electron correlations in nickelate superconductors, which can be controlled by modifying the block layers.
Article
Chemistry, Multidisciplinary
Takahiro Sawahara, Ryo Matsumoto, Yuki Nakahira, Hidetomo Usui, Noriyuki Kataoka, Ryusei Saitou, Takanori Wakita, Takayoshi Yokoya, Aichi Yamashita, Yosuke Goto, Yoshihiko Takano, Akira Miura, Yoshikazu Mizuguchi
Summary: Depending on thermal and pressure conditions, AgInS2 exhibits various crystal structures. In this study, trigonal AgInS2 was synthesized and found to be a semiconductor. The crystal structure was investigated through synchrotron powder X-ray diffraction and band calculation. The electrical resistance measurements under high pressure showed that the semiconducting behavior of AgInS2 was suppressed, but no metallic behavior was observed.
Article
Chemistry, Multidisciplinary
Taishi Noma, Hsiao-Yi Chen, Barun Dhara, Masato Sotome, Takuya Nomoto, Ryotaro Arita, Masao Nakamura, Daigo Miyajima
Summary: Researchers have found that the bulk photovoltaic effect (BPVE) in organic-inorganic hybrid perovskites (OIHPs) is not explained by the classical mechanism, but rather originates from the shift current mechanism. This discovery has significant implications for photodetector applications.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2023)
Article
Chemistry, Multidisciplinary
Tianchun Wang, Takuya Nomoto, Takashi Koretsune, Ryotaro Arita
Summary: We performed first-principles Eliashberg calculations for several conventional superconductors, investigating the importance of self-consistency in the calculation. By comparing the self-consistent results with the one-shot calculation results for the self-energy of electrons, we found that the difference between them becomes larger for systems with rapidly changing density of states around the Fermi level, such as those with van Hove singularities in pressurized hydrides.
JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS
(2023)
Article
Materials Science, Multidisciplinary
Shunsuke Kitou, Yoshio Kaneko, Yuiga Nakamura, Kunihisa Sugimoto, Yusuke Nomura, Ryotaro Arita, Yoshinori Tokura, Hiroshi Sawa, Taka-hisa Arima
Summary: By performing core differential Fourier synthesis (CDFS) analysis of high-energy X-ray diffraction data, we directly observe the distribution state of Mo 4d orbital electrons in a pyrochlore-type oxide Nd2Mo2O7 at subangstrom resolution. The obtained valence electron density (VED) distribution confirms the Mo4+ 4d2 orbital state, and a dip in the radial profile indicates a node of the 4d wave function. The VED distribution around the Nd site is attributed to the hybridization of neighboring O 2p with Nd 6s/6p/5d orbitals and the anisotropic Nd3+ 4f3 electrons, which cannot be explained by simple j-j or LS coupling models. This study demonstrates the usefulness of CDFS analysis in investigating orbital states in crystalline materials.
Article
Materials Science, Multidisciplinary
F. Schilberth, M. -C. Jiang, S. Minami, M. A. Kassem, F. Mayr, T. Koretsune, Y. Tabata, T. Waki, H. Nakamura, G. -Y. Guo, R. Arita, I. Kezsmarki, S. Bordacs
Summary: Through experimental and theoretical studies using broadband polarized reflectivity and magneto-optical Kerr effect spectroscopy, we have discovered giant anomalous Hall effect and magneto-optical activity in the magnet Co3Sn2S2 with topological nontrivial degeneracies, primarily generated by strongly tilted nodal-line segments around the Fermi energy. This finding is of significant importance for understanding the physical properties of magnetic topological materials.
Article
Materials Science, Multidisciplinary
Katsuhiro Tanaka, Takuya Nomoto, Ryotaro Arita
Summary: We investigate the tunneling magnetoresistance (TMR) effect using lattice models for magnetic tunnel junctions (MTJs). By analyzing the local density of states (LDOS) at the center of the barrier, we find that it qualitatively traces the TMR effect. The LDOS contains information on the electrodes and electron tunneling, allowing for a more precise evaluation of tunneling conductance. Furthermore, our findings show that the TMR effect in ferrimagnetic MTJs can be influenced by interfacial magnetic structures, which can also be captured by the LDOS.
Article
Materials Science, Multidisciplinary
Yuki Yanagi, Hiroaki Kusunose, Takuya Nomoto, Ryotaro Arita, Michi-To Suzuki
Summary: We propose a systematic method for generating symmetry-adapted magnetic structures to analyze complex modulated magnetic structures. The method extends the generation scheme based on multipole expansion, which was previously only applicable for k = 0. By mapping the multipole magnetic alignments to the periodic crystal structure with the phase factor for wave vector k, symmetry-adapted magnetic structures with ordering vector k can be obtained. This method provides all magnetic bases compatible with irreducible representations under a k group for a given crystal structure and wave vector k.
