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

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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confidence: 99%

“…1(d)]. [20,30,31]. After having determined the K-edge resonant energies for plane and apical oxygens [yz/zx A , xy P , and yz/zx P in Figs.…”

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confidence: 99%

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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

“…In the latter, it is the Coulomb-enhanced spin-orbit interaction, neglected in LDA+DMFT studies of the MIT so far, to actually induce the transition. Indeed, several works point to a relevant role of the spin-orbit coupling for the electronic structure of layered ruthenates [28][29][30][31][32]. To further complicate the picture, it was shown recently that, surprisingly, the effects of anisotropic Coulomb interactions-i.e., the terms with symmetry lower than O(3)-are crucial to reproduce the experimental Fermi surface of Sr 2 RuO 4 [30].…”

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confidence: 99%

Mott transition, spin-orbit effects, and magnetism in Ca2RuO4

Zhang

Pavarini

2017

In this work, we study the effects of spin-orbit and Coulomb anisotropy on the electronic and magnetic properties of the Mott insulator Ca 2 RuO 4 . We use the local-density approximation + dynamical mean-field approach and spin-wave theory. We show that, contrary to a recent proposal, the Mott metal-insulator transition is not induced by the spin-orbit interaction. We confirm that, instead, it is mainly driven by the change in structure from long to short c-axis layered perovskite. We show that the magnetic ordering and the anisotropic Coulomb interactions play a small role in determining the the size of the gap. The spin-orbit interaction turns out to be essential for describing the magnetic properties. It not only results in a spin-wave gap, but it also enlarges significantly the magnon bandwidth.

“…These orbitals are further mixed by spin-orbit coupling. [6][7][8] The exact superconducting gap structure in this material is an ongoing debate. [9][10][11] In spite of this, a few things can be said regarding the effective interactions between the low energy fermions on the three Fermi surfaces.…”

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confidence: 99%

Leggett modes and multiband superconductivity inSr2RuO4

Huang

Scaffidi²,

Sigrist

et al. 2016

Sr2RuO4 is a prototypical multi-band superconductor with three bands crossing the Fermi level. These bands exhibit distinct dimensional characteristics, with one quasi-2D γ-band and two quasi-1D α-and β-bands. This leads to the expectation that the superconductivity on the γ-band may be only weakly Josephson-coupled to that on the other two bands. Based on an explicit microscopic weak coupling calculation appropriate for Sr2RuO4, we study the collective Leggett modes associated with the relative phase oscillations between the bands and show that a relatively soft Leggett mode exists due to the comparatively weaker inter-band Josephson coupling. These calculations also provide insight into why the superconducting gap magnitudes may be comparable on all three bands, despite the noticeable differences between the γ and α/β bands. The analyses can be readily applied to other multi-band superconductors.Multi-band superconductors possess physical properties that are not present in single-band superconductors. Depending on the nature of the interactions driving the Cooper pairing and the orbital character of the bands, the superconducting order parameter may not be dominated by one band with only much weaker induced superconductivity on the other bands. This is particularly so in multi-band systems with unconventional pairing symmetry, where the correlations underlying the superconductivity often involve electrons on different bands strongly interacting with each other. These inter-band interactions give rise to effective Josephson couplings between the superconducting order parameters of the different bands 1 . As a consequence, in the ground state, the multiple order parameters are locked in a configuration with a particular set of relative phases and magnitudes.Under external perturbations or at finite temperatures, the relative phase between the multiple order parameters can fluctuate, costing a finite amount of energy that is determined by the inter-band couplings. These collective excitations are commonly referred to as Leggett modes.1 They respond to electromagnetic fields in a peculiar manner, and are unlike the usual global U(1) phase fluctuations which are pushed up to the plasma frequency due to Coulomb interactions. 2 The putative chiral p-wave superconductor Sr 2 RuO 4 3-5 is a prototypical multi-band system, with three bands crossing the Fermi energy -two quasi one dimensional (1D) α/β-bands and one quasi two dimensional (2D) γ-band (Fig. 1). 9The quasi-1D bands originate primarily from the hybridized 4d xz and yz-orbitals, while the γ-band is dominated by the xy-orbital. These orbitals are further mixed by spin-orbit coupling. [6][7][8] The exact superconducting gap structure in this material is an ongoing debate. [9][10][11] In spite of this, a few things can be said regarding the effective interactions between the low energy fermions on the three Fermi surfaces. Firstly, the intraband Cooper pair scattering on the quasi-1D bands may be markedly different from that on the quasi-2D band. This could lead ...