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

遠山 貴己; 森 道康; 曽田 繁利*

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

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 .

Theoretical study of electronic states and excitation spectra in Ni-substituted cuprates

筒井 健二; 遠山 貴己*; 前川 禎通

JPS Conference Proceedings (Internet), 3, p.017008_1 - 017008_6, 2014/06

https://doi.org/10.7566/JPSCP.3.017008

銅酸化物高温超伝導物質における不純物置換効果の研究がこれまで世界中で数多く研究されている。Ni不純物置換に対してキャリアがNi不純物近傍へ局在化するといった興味深い現象が実験及び理論的研究により明らかになってきている。本研究ではクラスター計算によって、不純物濃度に比べてホール濃度が高い場合の電子状態を議論し、共鳴非弾性X線散乱スペクトルの予見を行った。

High-energy spin and charge excitations in electron-doped copper oxide superconductors

石井 賢司; 藤田 全基*; 佐々木 隆了*; Minola, M.*; Dellea, G.*; Mazzoli, C.*; Kummer, K.*; Ghiringhelli, G.*; Braicovich, L.*; 遠山 貴己*; et al.

Nature Communications (Internet), 5, p.3714_1 - 3714_8, 2014/04

https://doi.org/10.1038/ncomms4714

We combine X-ray and neutron inelastic scattering measurements to track the doping dependence of both spin and charge excitations in electron-doped materials. Copper resonant inelastic X-ray scattering spectra show that magnetic excitations shift to higher energy upon doping. Their dispersion becomes steeper near the magnetic zone center and they deeply mix with charge excitations, indicating that electrons acquire a highly itinerant character in the doped metallic state. Moreover, above the magnetic excitations, an additional dispersing feature is observed near the -point, and we ascribe it to particle-hole charge excitations. These properties are in stark contrast with the more localized spin-excitations (paramagnons) recently observed in hole-doped compounds even at high doping-levels.

Spin dynamics and resonant inelastic X-ray scattering in chromium with commensurate spin-density wave order

杉本 高大*; Li, Z.*; 兼下 英司*; 筒井 健二; 遠山 貴己*

Physical Review B, 87(13), p.134418_1 - 134418_8, 2013/04

https://doi.org/10.1103/PhysRevB.87.134418

多軌道系反強磁性金属であるクロム金属のスピン励起スペクトルと共鳴非弾性X線散乱スペクトルを理論的に予見した。スペクトルの計算に際し、多軌道ハバード模型に対する平均場近似及び乱雑位相近似を行い、またX線散乱プロセスに対して高速衝突近似を行った。その結果、スピン励起に関しては、0.6eV以上で集団励起であるマグノン励起がほとんど強度を持たず、代わりに個別励起のエネルギー的に広がったスペクトルが支配的になることがわかった。

Inelastic X-ray scattering studies of electronic excitations

石井 賢司; 遠山 貴己*; 水木 純一郎

Journal of the Physical Society of Japan, 82(2), p.021015_1 - 021015_24, 2013/02

https://doi.org/10.7566/JPSJ.82.021015

Inelastic X-ray Scattering (IXS) has developed as one of the most powerful momentum-resolved spectroscopies. Especially in the last decade, it achieved significant progress by utilizing brilliant X-rays from third generation synchrotron radiation facilities. Simultaneously, theoretical efforts have been made to predict or interpret the experimental spectra. One of the scientific fields studied intensively by means of IXS is strongly correlated electron systems, where the interplay of charge, spin, and orbital degrees of freedom determines their physical properties. IXS can provide a new insight into electron dynamics of the systems through the observation of charge, spin, and orbital excitations. Focusing on the momentum-resolved electronic excitations in strongly correlated electron systems, we review IXS studies and present capabilities of IXS for the study of dynamics of materials.

Electronic excitations around the substituted atom in LaCuNO as seen via resonant inelastic X-ray scattering

石井 賢司; 筒井 健二; 池内 和彦*; Jarrige, I.; 水木 純一郎; 平賀 晴弘*; 山田 和芳*; 遠山 貴己*; 前川 禎通; 遠藤 康夫*; et al.

Physical Review B, 85(10), p.104509_1 - 104509_5, 2012/03

https://doi.org/10.1103/PhysRevB.85.104509

We perform a resonant inelastic X-ray scattering (RIXS) study of Ni-substituted LaCuO and Cu-substituted LaNiO.Resonantly enhanced charge-transfer excitations are successfully observed by tuning the incident photon energy to the -edge of the substituted element. These excitations display a very weak momentum dependence, evidencing their local character. We find a shift in the energy of the onset edge of these features compared with the non-substituted compounds LaCuO and LaNiO. This shift is quantitatively reproduced by exact diagonalization calculations of the RIXS spectra. RIXS is shown to be a powerful tool to probe the electronic states of substituted elements and to understand their interaction with surrounding atoms.

Quantum dynamics of a driven correlated system coupled to phonons

Vidmar, L.*; Bona, J.*; 遠山 貴己; 前川 禎通

Physical Review Letters, 107(24), p.246404_1 - 246404_4, 2011/12

https://doi.org/10.1103/PhysRevLett.107.246404

Nonequilibrium interplay between charge, spin, and lattice degrees of freedom on a square lattice is studied for a single charge carrier doped in the --Holstein model. In the presence of a static electric field we calculate the quasistationary state. With increasing electron-phonon (e-ph) coupling the carrier mobility decreases; however, we find increased steady state current due to e-ph coupling in the regime of negative differential resistance. We explore the distribution of absorbed energy between the spin and the phonon subsystem. For model parameters as relevant for cuprates, the majority of the gained energy flows into the spin subsystem.

Theoretical study of resonant inelastic X-ray scattering spectrum in the Hubbard ladder

筒井 健二; 遠山 貴己*; 前川 禎通*

Physica C, 470(Suppl.1), p.S232 - S233, 2010/12

https://doi.org/10.1016/j.physc.2009.10.042

梯子格子系銅酸化物の銅K吸収端共鳴非弾性X線散乱スペクトルを、数値的厳密対角化法を用いて計算した。これまでに梯子格子系における散乱スペクトルの運動量依存性に、基底状態におけるスピン・シングレット状態の形成状態と関係していることが示唆された。一方で梯子の対角方向に沿ったホールの飛び移りの符号により、スピン・シングレット状態の形成強度が劇的に変化することが明らかになっている。そこで本研究では共鳴非弾性X線散乱スペクトルの形状とスピン・シングレット状態の関係をより明確にするために、梯子の対角方向に沿ったホールの飛び移りを加えてスペクトルの変化を調べた。その結果、実際に状態とスペクトルが関係することを明らかにした。

Temperature dependence of the electronic structure of SrCuO studied by resonant inelastic X-ray scattering

吉田 雅洋; 石井 賢司; 池内 和彦*; Jarrige, I.; 村上 洋一*; 水木 純一郎; 筒井 健二; 遠山 貴己*; 前川 禎通*; 工藤 一貴*; et al.

Physica C, 470(Suppl.1), p.S145 - S146, 2010/12

https://doi.org/10.1016/j.physc.2009.11.082

SrCaCuO (SCCO), which is composed of two-leg ladders and edge-sharing chains, is the first superconducting cuprate without CuO planes. By substituting Ca for Sr, holes are transferred from the chains to the ladders. It was recently shown that charge ordering (CO) along the leg direction in the ladder occurs at and the periodicity is five times the unit length along the c axis. In order to investigate the electronic excitations associated with the CO, we carried out resonant inelastic X-ray scattering (RIXS) experiments for SCCO (). Cu- RIXS can directly probe the momentum-dependent electronic excitations related to the Cu site, which are resonantly enhanced by tuning the incident photon energy to the Cu -edge. We measured the q dependence of the intraband excitations, which is associated with the dynamics of doped holes in the Zhang-Rice singlet band. The intensity is enhanced at the momentum corresponding to the periodicity of the CO in , while the temperature dependence of the enhancement is different for and . We discuss the relationship between our experimental results and the occurrence of the CO.

Effect of Fermi surface topology on inter-layer magnetoresistance in layered multiband systems; Application to LaFeAsOF

森成 隆夫*; 中村 博樹; 町田 昌彦; 遠山 貴己*

Journal of the Physical Society of Japan, 78(11), p.114702_1 - 114702_7, 2009/11

https://doi.org/10.1143/JPSJ.78.114702

In layered single band systems, the interlayer conductivity depends on the orientation of the in-plane magnetic field and takes maximum values when the magnetic field is perpendicular to flat regions of the Fermi surface. Extending this known results to multi-band systems, we propose an experiment to extract information about their Fermi surface topology. We discuss application of the formula to a FeAs-based superconductor, LaFeAsOF. We show that the magnetically ordered state in the parent compound is clearly distinguished from the paramagnetic state by the oscillation period in the interlayer conductivity. We demonstrate that evolution of the Fermi surface topology by changing the doping concentration is reflected to the interlayer conductivity oscillation patterns.