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藤原 理賀*; 森田 克洋*; Mole, R.*; 満田 節生*; 遠山 貴巳*; 矢野 真一郎*; Yu, D.*; 曽田 繁利*; 桑井 智彦*; 幸田 章宏*; et al.
Nature Communications (Internet), 11, p.3429_1 - 3429_7, 2020/07
被引用回数：37 パーセンタイル：90.63(Multidisciplinary Sciences)Observation of a quantum spin liquid (QSL) state is one of the most important goals in condensed-matter physics, as well as the development of new spintronic devices that support next-generation industries. The QSL in two-dimensional quantum spin systems is expected to be due to geometrical magnetic frustration, and thus a kagome-based lattice is the most probable playground for QSL. Here, we report the first experimental results of the QSL state on a square-kagome quantum antiferromagnet, KCu
AlBiO
(SO)
Cl. Comprehensive experimental studies via magnetic susceptibility, magnetisation, heat capacity, muon spin relaxation, and inelastic neutron scattering measurements reveal the formation of a gapless QSL at very low temperatures close to the ground state. The QSL behavior cannot be explained fully by a frustrated Heisenberg model with nearest-neighbor exchange interactions, providing a theoretical challenge to unveil the nature of the QSL state.
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遠山 貴己; 森 道康; 曽田 繁利*
Physical Review B, 97(23), p.235137_1 - 235137_7, 2018/06
被引用回数：10 パーセンタイル：45.99(Materials Science, Multidisciplinary)We investigate the dynamical spin and charge structure factors of the -- four-leg ladder by using dynamical density-matrix renormalization group. The dynamical charge structure factor along the momentum direction from 
to 
clearly shows low-energy excitations corresponding to the stripe order in hole doping. On the other hand, the stripe order weakens in electron doping, resulting in less low-energy excitations in the charge channel. In spin channel, we find incommensurate spin excitations near 
forming a hour-glass behavior in hole doping, while in electron doping we find clearly spin-wave-like dispersions starting from . Along the 
- direction, the spin excitations are strongly influenced by the stripes in hole doping, resulting in two branches that form a discontinuous behavior in the dispersion. In contrast, the electron-doped systems show a downward shift in energy toward .
edge石井 賢司*; 遠山 貴巳*; 浅野 駿*; 佐藤 研太朗*; 藤田 全基*; 脇本 秀一; 筒井 健二*; 曽田 繁利*; 宮脇 淳*; 丹羽 秀治*; et al.
Physical Review B, 96(11), p.115148_1 - 115148_8, 2017/09
被引用回数：29 パーセンタイル：77.9(Materials Science, Multidisciplinary)We investigate electronic excitations in La
(Br,Sr)
CuO using resonant inelastic X-ray scattering (RIXS) at the oxygen edge. We observed momentum-dependent spectral weight below 1 eV, which is consistent with theoretical calculation of the dynamical charge structure factor on oxygen orbitals in a three-band Hubbard model. Our results confirm that the momentum-dependent charge excitations exist on the order of the transfer energy (), and the broad spectral line shape indicates damped and incoherent character of the charge excitations at the energy range in the doped Mott insulators.
遠山 貴巳*; 筒井 健二; 森 道康; 曽田 繁利*; 柚木 清司*
Physical Review B, 92(1), p.014515_1 - 014515_8, 2015/07
被引用回数：14 パーセンタイル：52.39(Materials Science, Multidisciplinary)銅L吸収端共鳴非弾性X線散乱は銅酸化物高温超伝導物質の電荷励起を調べる強力な手法である。この散乱手法による電荷の集団励起の観測可能性を理論的に調べる。散乱プロセスにおける中間状態を経ることで必然的に電子ドープ系の電荷集団励起モードの強度がホールドープ系よりも強くなる。この電子・ホール非対称性は動的電荷構造因子にも現れる。特に電子ドープ系において低運動量変化の低エネルギー領域に新たな増強された励起モードとして現れる。これらの結果は電子ドープ系の新しい電荷励起モードの共鳴非弾性X線散乱による観測可能性を示している。
松枝 宏明*; 曽田 繁利*; 遠山 貴己*; 前川 禎通
Journal of the Physical Society of Japan, 81(1), p.013701_1 - 013701_4, 2012/01
被引用回数：39 パーセンタイル：82.98(Physics, Multidisciplinary)We examine recombination processes of photocarriers in one-dimensional Mott insulators coupled to phonons. Performing density matrix renormalization group calculations, we find that, even for small electron, phonon coupling, many phonons are generated dynamically, which cause initial relaxation process after the irradiation. At the same time, spin charge coupling coming from mixing of high- and low-energy states by the irradiation is suppressed. We discuss differences between Mott and band insulators in terms of relaxation dynamics.
