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Bisogni, Valentina; Sala, M. Moretti; Bendounan, A.; Brookes, N. B.; Ghiringhelli, G.; Braicovich, L.

doi:10.1103/physrevb.85.214528

Cited by 28 publications

(19 citation statements)

References 13 publications

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“…This feature can be attributed to bimagnons, because (1) their energy scales are consistent with the bimagnons (160 meV for Sr 2 IrO 4 and 185 meV for Sr 3 Ir 2 O 7 ) measured by Raman scattering [47] and (2) their dispersions are in agreement with those measured by Ir L 3 RIXS [16][17][18]. Note that the bimagnons of cuprates measured by O K RIXS are nondispersive [35,36]. The presence of both single magnons and bimagnons indicates that O K RIXS is a powerful spectroscopic method for studying the magnetic dynamics of iridates.…”

supporting

confidence: 72%

“…Therefore, soft x-ray RIXS is a promising method for studying artificial two-dimensional samples [7,8]. However, given that SOC is absent in the O 1s level, O K RIXS is expected to be insensitive to single spin-flip excitations [31,35,36]. This would severely limit the applicability of O K RIXS on iridates and related 5d TM oxides, especially thin films and heterostructures fabricated by these materials, where magnetic excitations need to be studied for probing the low-energy Hamiltonian [15][16][17][18].…”

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confidence: 99%

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Dispersive magnetic and electronic excitations in iridate perovskites probed by oxygen K -edge resonant inelastic x-ray scattering

Olalde-Velasco

Huang

et al. 2018

Phys. Rev. B

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Resonant inelastic x-ray scattering (RIXS) experiments performed at the oxygen K edge on the iridate perovskites Sr 2 IrO 4 and Sr 3 Ir 2 O 7 reveal a sequence of well-defined dispersive modes over the energy range up to ∼0.8 eV. The momentum dependence of these modes and their variation with the experimental geometry allows us to assign each of them to specific collective magnetic and/or electronic excitation processes, including single and bimagnons, and spin-orbit and electron-hole excitons. We thus demonstrate that dispersive magnetic and electronic excitations are observable at the O K edge in the presence of the strong spin-orbit coupling in the 5d shell of iridium and strong hybridization between Ir 5d and O 2p orbitals, which confirm and expand theoretical expectations. More generally, our results establish the utility of O K-edge RIXS for studying the collective excitations in a range of 5d materials that are attracting increasing attention due to their novel magnetic and electronic properties. Especially, the strong RIXS response at O K edge opens up the opportunity for investigating collective excitations in thin films and heterostructures fabricated from these materials. DOI: 10.1103/PhysRevB.97.041102 Characterizing the elementary excitations in correlated electron systems is an essential prerequisite for obtaining a complete understanding of the underlying electronic interactions and therefore crucial for revealing the origin of emergent phases [1,2]. Resonant inelastic x-ray scattering (RIXS) has become established in the past decade as a powerful tool for studying the momentum dependence of electronic and magnetic excitations [2]

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supporting

confidence: 72%

mentioning

confidence: 99%

Dispersive magnetic and electronic excitations in iridate perovskites probed by oxygen K -edge resonant inelastic x-ray scattering

Olalde-Velasco

Huang

et al. 2018

Phys. Rev. B

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“…[34][35][36][37]54,55] in the case of the Heisenberg model, consistent with our UCL expansions for the Hubbard and t − J models. Note that usually the Green's functions containing the two-spin and the threespin operators are referred to as probing the "two-magnon" and the "three-magnon" spectrum, though this terminology may be used loosely in this context.…”

Section: Appendix B: Ucl Approximation For the T − J Modelsupporting

confidence: 63%

“…The fast collision approximation [28][29][30] and the effective operator approach [31] suggested that only single magnon excitations or Sðq; ωÞ should be measured by RIXS at the Cu L edge [27,31,32]. More sophisticated treatments-the ultrashort core-hole lifetime (UCL) expansion [33][34][35] and the UCL-inspired ansatz [36]-highlighted that RIXS should also be sensitive to bimagnon excitations. A further extension of UCL also pointed out the importance of three-magnon excitations [37].…”

Section: When ∼10mentioning

confidence: 99%

Using RIXS to Uncover Elementary Charge and Spin Excitations

et al. 2016

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Despite significant progress in resonant inelastic x-ray scattering (RIXS) experiments on cuprates at the Cu L-edge, a theoretical understanding of the cross section remains incomplete in terms of elementary excitations and the connection to both charge and spin structure factors. Here, we use state-of-the-art, unbiased numerical calculations to study the low-energy excitations probed by RIXS in the Hubbard model, relevant to the cuprates. The results highlight the importance of scattering geometry, in particular, both the incident and scattered x-ray photon polarization, and they demonstrate that on a qualitative level the RIXS spectral shape in the cross-polarized channel approximates that of the spin dynamical structure factor. However, in the parallel-polarized channel, the complexity of the RIXS process beyond a simple two-particle response complicates the analysis and demonstrates that approximations and expansions that attempt to relate RIXS to less complex correlation functions cannot reproduce the full diversity of RIXS spectral features.

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“…bi-magnon) scattering -are allowed [17][18][19]. Indeed bi-magnon scattering is observed both at TM [20,21] and oxygen (O) K-edges [22,23]. This apparent absence of single-magnon spin-flip scattering is unfortunate because the O K-edge is in a soft x-ray regime where the RIXS resolution is particularly high (even if in this situation only a limited part of momentum space is accessible) and oxygen anions are obviously ubiquitous in magnetic materials.…”

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confidence: 99%

Resonant inelastic x-ray scattering on single magnons at oxygenKedges

Kim

Brink

2015

Phys. Rev. B

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The recent discovery that resonant inelastic x-ray scattering can probe single-magnon (SM) dispersions in transition metal (TM) oxides when the x-ray energy is tuned to the TM L-edge, has put this technique on a par with inelastic neutron scattering. It is generally presumed that selection rules forbid SM-scattering at oxygen (O) K-edges. However, based on a symmetry analysis and exact diagonalization study, we show that SM-scattering at O K-edges becomes allowed when (i) spin-orbit coupling is present in the TM d-shell and (ii) inversion symmetry at the O-site is broken. For cuprates the resulting SM-amplitude is very weak but in iridates both prerequisites can amply be fulfilled.PACS numbers: 75.30. Ds,78.70.Ck,71.70.Ej Introduction -The theoretical prediction [1] and subsequent experimental observation [2,3] that the dispersion of magnetic excitations, in particular of elementary single-magnons, can be measured directly by resonant inelastic x-ray scattering (RIXS) has fundamentally changed the field of inelastic magnetic scattering [4]. It has for instance lead to the discovery of distinct paramagnons in a large family of high-temperature cuprate superconductors [3][4][5][6][7][8], and established the presence of strongly dispersive magnetic modes in a number of iridium oxides [9][10][11][12].All these efforts to extract the dispersion of elementary magnetic excitations from RIXS have focussed on the transition metal (TM) L-edge, where single spin-flip scattering is directly allowed [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. The microscopic origin of this type of magnetic scattering is rather straightforward. When energy in RIXS the incoming photon is tuned to a TM L-edge, an electron with spin σ is excited out of the atomic p-shell, deep inside the atomic core, into the TM d-shell. The core-hole that is created in this event can now flip its spin due its very large spin-orbit interaction. Subsequently a valence d electron with spin −σ can fill the core-hole and an outgoing x-ray is emitted. The net result of this RIXS process is a spin-flip transition σ → −σ in the TM d-shell, which is the same as the net result of inelastic neutron scattering involving this d-shell electron.When a K-edge is used instead of a L-edge, this direct spin-flip process is no longer allowed. This is because in K-edge RIXS an electron is excited from a core-shell with s-symmetry, for which spin-orbit coupling is simply absent. It thus appears that for RIXS at K-edges direct spin-flip scattering is forbidden and only higher order magnetic scattering processes -starting at double spin-flip (e.g. bi-magnon) scattering -are allowed [17][18][19]. Indeed bi-magnon scattering is observed both at TM [20,21] and oxygen (O) K-edges [22,23]. This apparent absence of single-magnon spin-flip scattering is unfortunate because the O K-edge is in a soft x-ray regime where the RIXS resolution is particularly high (even if in this situation only a limited part of momentum space is accessible) and oxygen anions are obviously ubiquito...

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Bimagnon studies in cuprates with resonant inelastic x-ray scattering at the OKedge. II. Doping effect in La2−xSrx<

Cited by 28 publications

References 13 publications

Dispersive magnetic and electronic excitations in iridate perovskites probed by oxygen K -edge resonant inelastic x-ray scattering

Dispersive magnetic and electronic excitations in iridate perovskites probed by oxygen K -edge resonant inelastic x-ray scattering

Using RIXS to Uncover Elementary Charge and Spin Excitations

Resonant inelastic x-ray scattering on single magnons at oxygenKedges

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