Femtosecond Dynamics of Momentum-Dependent Magnetic Excitations from Resonant Inelastic X-Ray Scattering inCaCu2O3

Abstract

Taking spinon excitations in the quantum antiferromagnet CaCu2O3 as an example, we demonstrate that femtosecond dynamics of magnetic electronic excitations can be probed by direct resonant inelastic x-ray scattering (RIXS). To this end, we isolate the contributions of single and double spin-flip excitations in experimental RIXS spectra, identify the physical mechanisms that cause them, and determine their respective time scales. By comparing theory and experiment, we find that double spin flips need a finite amount of time to be generated, rendering them sensitive to the core-hole lifetime, whereas single spin flips are, to a very good approximation, independent of it. This shows that RIXS can grant access to time-domain dynamics of excitations and illustrates how RIXS experiments can distinguish between excitations in correlated electron systems based on their different time dependence.

Extending resonant inelastic X-ray scattering to the extreme ultraviolet

“…Shake-up excitations include double magnons (see Discussion in Bisogni et al [28]) and charge transfer excitations at the M-and L-edges (see Figure 4 below), and can have a distinctive pattern of incident energy dependence in RIXS spectra [8]. These excitations have a fractional contribution to scattering intensity in the RIXS spectrum that scales roughly as I ∼ K 2 / Ŵ 2 when core hole lifetime is short (|K/ Ŵ| ≪ 1) due to destructive interference in the numerator of the Kramers-Heisenberg scattering equation (see discussion of "indirect" RIXS in Ament et al [4]).…”

“…The lifetime of shallow core hole resonance states accessed in the EUV has a complex dependence on incident photon energy [6,[31][32][33], and can provide the option to access both long and short core hole lifetimes at the same resonance edge. The effective shake-up perturbation caused by shallow core holes also tends to be weaker, and can exclude some classes of excitations that are not directly created by the action of the scattering photon operators (e.g., multi-magnons, phonons, charge transfer modes) [3,4,7,8,10,28,34,35]. Atomic multiplet (AM) models of RIXS can potentially work better in the EUV, because angular momentum entanglement through multipolar Coulomb interactions is stronger than at the L-edge, and protects multiplet symmetries.…”

Ba4[Mn3N6], a Quasi-One-Dimensional Mixed-Valent Nitridomanganate (II, IV)

“…Therefore, the electronic state of the constituting magnetic atoms, along with the magnetic topology, determines the behavior of a particular system. Low-dimensional quantum magnets have been mainly explored in the families of halides [6], oxides [7], and higher chalcogenides [8], but little is known about the realization of such systems in nitrides. Since multicomponent nitrides often demonstrate low-dimensional crystallographic arrangements of transition-metal atoms along with low coordination numbers and oxidation states of the latter [9][10][11], they represent a natural platform to probe low-dimensional magnetism.…”

Experimental signatures of phase interference and subfemtosecond time dynamics on the incident energy axis of resonant inelastic x-ray scattering

“…The latter case, which we will call "shake-up" RIXS applies to the non-pre-edge features at the transition metal K-edge [1,2,4,5,9], and includes principle scattering channels for double magnon (see discussion in Ref. [24]) and charge transfer excitations at the M-and L-edges. Because m f |T † |m m|T |g = 0 for shake-up RIXS, these excitations must have fully destructive path phase interference, and their fractional contribution to scattering intensity in the RIXS spectrum scales as I ∼ K fractional intensity of shake-up excitations converges on a fixed value and phase interference goes from destructive to neutral in Eq.…”

“…In resonant inelastic X-ray scattering (RIXS), core hole resonance modes are used to enhance coupling between photons and low energy electronic degrees of freedom, resulting in inelastic spectral features that typically include more than one overlapping excitation symmetry. These final states of RIXS include modes that are of broad fundamental interest, such as momentum-dependent Mott gap transitions and emergent particles composed of diverse combinations of charge, orbital and spin degrees of freedom [1][2][3][4][5][6][7][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24].…”