Spin-orbit-induced orbital excitations in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mtext>Sr</mml:mtext><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mtext>RuO</mml:mtext><mml:mn>4</mml:mn></mml:msub></mml:mrow></mml:math>and<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mtext>Ca</mml:mtext><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mtext>RuO</mml:mtext><mml:mn>4</mml:mn></mml:msub></mml:mrow></mml:math>: A resonant inelastic x-ray sc

Fatuzzo, C. G.; Dantz, Marcus; Fatale, Sara; Olalde-Velasco, P.; Shaik, N. E.; Piazza, B. Dalla; Tóth, S.; Pelliciari, Jonathan; Fittipaldi, R.; Vecchione, A.; Kikugawa, Naoki; Brooks, J. S.; Rønnow, Henrik M.; Grioni, M.; Rüegg, Ch.; Schmitt, Thorsten; Chang, J.

doi:10.1103/physrevb.91.155104

Cited by 54 publications

(45 citation statements)

References 42 publications

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“…The ground-state wave function of the Ru 4+ ion was described in terms of an admixture of xy, yz, and zx orbitals, whose respective contribution depends on the relative strength of the tetragonal crystal field δ and SOC λ [20,[48][49][50][51][52][53]. Within this picture, the tuning of the crystal field caused by the elongation of the RuO 6 octahedra [ Fig.…”

Section: Discussionmentioning

confidence: 99%

Persistence of antiferromagnetic order upon La substitution in the 4d4 Mott insulator Ca2RuO4

et al. 2018

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The chemical and magnetic structures of the series of compounds Ca 2−x La x RuO 4 [x = 0, 0.05(1), 0.07(1), 0.12(1)] have been investigated using neutron diffraction and resonant elastic x-ray scattering. Upon La doping, the low-temperature S-P bca space group of the parent compound is retained in all insulating samples [x 0.07(1)], but with significant changes to the atomic positions within the unit cell. These changes can be characterized in terms of the local RuO 6 octahedral coordination: with increasing doping, the structure, crudely speaking, evolves from an orthorhombic unit cell with compressed octahedra to a quasitetragonal unit cell with elongated ones. The magnetic structure on the other hand, is found to be robust, with the basic k = (0,0,0), b-axis antiferromagnetic order of the parent compound preserved below the critical La doping concentration of x ≈ 0.11. The only effects of La doping on the magnetic structure are to suppress the A-centred mode, favoring the B mode instead, and to reduce the Néel temperature somewhat. Our results are discussed with reference to previous experimental reports on the effects of cation substitution on the d 4 Mott insulator Ca 2 RuO 4 , as well as with regard to theoretical studies on the evolution of its electronic and magnetic structure. In particular, our results rule out the presence of a proposed ferromagnetic phase, and suggest that the structural effects associated with La substitution play an important role in the physics of the system.

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Section: Discussionmentioning

confidence: 99%

Persistence of antiferromagnetic order upon La substitution in the 4d4 Mott insulator Ca2RuO4

et al. 2018

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“…Ca 2 RuO 4 has attracted considerable attention in recent years as the Mott-insulating analogue of the unconventional superconductor Sr 2 RuO 4 [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] . A welldocumented metal to insulator transition (MIT) occurs at T MIT = 357 K, concomitant with a first-order structural transition from a high-temperature quasitetragonal phase to a low-temperature orthorhombic one (P bca space group) 1,2,4,17 .…”

Section: Introductionmentioning

confidence: 99%

“…The coupling between lattice and orbital degrees of freedom was highlighted by recent X-ray near-edge absorption spectroscopy (XANES) studies 5,10,15 , which revealed that the ground-state t 2g orbital population can be effectively tuned by changing the ratio ∆/λ, analogous to the case of the Ir 4+ ion in perovsite iridates 24 . The low-energy electronic structure is thus expected to be extremely sensitive to structural distortions acting on the local Ru 4+ crystalline environment.…”

Section: Introductionmentioning

confidence: 99%

Tuning of the Ru4+ ground-state orbital population in the 4d4 Mott insulator C

et al. 2019

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The ground-state orbital occupancy of the Ru 4+ ion in Ca2−xLaxRuO4 [x = 0, 0.05(1), 0.07(1) and 0.12(1)] was investigated by performing X-ray absorption spectroscopy (XAS) in the vicinity of the O K edge as a function of angle between the incident beam and the surface of the single-crystal samples. A minimal model of the hybridization between the O 2p states probed at the K edge and the Ru 4d orbitals was used to analyze the XAS data, allowing the ratio of hole occupancies nxy/nyz,zx to be determined as a function of doping and temperature. For the samples displaying a low-temperature insulating ground-state (x ≤ 0.07), nxy/nyz,zx is found to increase significantly with increasing doping, with increasing temperature acting to further enhance nxy/nyz,zx. For the x = 0.12 sample, which has a metallic ground-state, the XAS spectra are found to be independent of temperature, and not to be describable by the minimal hybridization model, while being qualitatively similar to the spectra displayed by the x ≤ 0.07 samples above their insulating to metallic transitions. To understand the origin of the evolution of the electronic structure of Ca2−xLaxRuO4 across its phase diagram, we have performed theoretical calculations based on a model Hamiltonian, comprising electron-electron correlations, crystal field (∆) and spin-orbit coupling (λ), of a Ru-O-Ru cluster, with realistic values used to parameterize the various interactions taken from the literature. Our calculations of the Ru hole occupancy as a function of ∆/λ provide an excellent description of the general trends displayed by the data. In particular they establish that the enhancement of nxy/nyz,zx is driven by significant modifications to the crystal field as the tetragonal distortion of the RuO6 octahedral changes from compressive to tensile with La doping. We have also used our model to show that the hole occupancy of the O 2p and Ru 4d orbitals display the same general trend as a function of ∆/λ, thus validating the minimal hybridization model used to analyze the data. In essence, our results suggest that the predominant mechanism driving the emergence of the low-temperature metallic phase in La doped Ca2RuO4 is the structurally induced redistribution of holes within the t2g orbitals, rather that the injection of free carriers.

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“…RIXS is therefore an attractive complementary technique to neutron scattering. This has, in particular, lead to progress in understanding correlated low-dimensional 3d,4d, and 5d electron systems [11][12][13]. The spin-excitation spectra of insulating one-and two-dimensional cuprates have, for example, been studied by soft x-ray RIXS using the copper L 3 edge [12,[14][15][16][17][18][19].…”

Section: Introductionmentioning

confidence: 99%

Resonant inelastic x-ray scattering study of the spin and charge excitations in the overdoped superconductorLa1.77Sr0.23CuO4

et al. 2016

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We present a resonant inelastic x-ray scattering (RIXS) study of spin and charge excitations in overdoped La 1.77 Sr 0.23 CuO 4 along two high-symmetry directions. The line shape of these excitations is analyzed and they are shown to be highly overdamped. Their spectral weight and damping are found to be strongly momentum dependent. Qualitative agreement between these observations and a calculated random-phase approximation susceptibility is obtained for this overdoped compound, implying that a significant contribution to the RIXS signal stems from a continuum of charge excitations. Furthermore, this suggests that the spin excitations in the overdoped regime can be captured qualitatively by an itinerant picture. Our calculations also predict a low-energy spin-excitation branch to exist along the nodal direction near the zone center. With the energy resolution of the present experiment, this branch is not resolvable, but we show that the next generation of high-resolution spectrometers will be able to test this prediction.

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Spin-orbit-induced orbital excitations inSr2RuO4andCa2RuO4: A resonant inelastic x-ray sc

Cited by 54 publications

References 42 publications

Persistence of antiferromagnetic order upon La substitution in the 4d4 Mott insulator Ca2RuO4

Persistence of antiferromagnetic order upon La substitution in the 4d4 Mott insulator Ca2RuO4

Tuning of the Ru4+ ground-state orbital population in the 4d4 Mott insulator C

Resonant inelastic x-ray scattering study of the spin and charge excitations in the overdoped superconductorLa1.77Sr0.23CuO4

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