Time-resolved resonant inelastic x-ray scattering in a pumped Mott insulator

Manipulating spin fluctuations with ultrafast laser pulses is a promising route to dynamically control collective phenomena in strongly correlated materials. However, understanding how photoexcited spin degrees of freedom evolve at a microscopic level requires a momentum- and energy-resolved characterization of their nonequilibrium dynamics. Here, we study the photoinduced dynamics of finite-momentum spin excitations in two-dimensional Mott insulators on a square lattice. By calculating the time-resolved resonant inelastic x-ray scattering cross-section, we show that an ultrafast pump above the Mott gap induces a prompt softening of the spin excitation energy, compatible with a transient renormalization of the exchange interaction. While spin fluctuations in a hole-doped system (paramagnons) are well described by Floquet theory, magnons at half filling are found to deviate from this picture. Furthermore, we show that the paramagnon softening is accompanied by an ultrafast suppression of d-wave pairing correlations, indicating a link between the transient spin excitation dynamics and superconducting pairing far from equilibrium.

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“…The trRIXS cross-section at a direct absorption edge can be written as 35,36 (see Supplementary Note 1 for further details)…”

Section: Resultsmentioning

confidence: 99%

X-ray scattering from light-driven spin fluctuations in a doped Mott insulator

et al. 2021

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“…Finally, we point out that time-resolved XAS [79,80] can be used to monitor hole distribution among different orbitals when driven by c-axis polarized fields as an experimental validation of this photodoping effect.…”

Section: Discussion and Summarymentioning

confidence: 91%

Orbitally selective resonant photodoping to enhance superconductivity

et al. 2021

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Signatures of superconductivity at elevated temperatures above Tc in high temperature superconductors have been observed near 1/8 hole doping for photoexcitation with infrared or optical light polarized either in the CuO2-plane or along the c-axis. While the use of in-plane polarization has been effective for incident energies aligned to specific phonons, c-axis laser excitation in a broad range between 5 µm and 400 nm was found to affect the superconducting dynamics in striped La1.885Ba0.115CuO4, with a maximum enhancement in the 1/ω dependence to the conductivity observed at 800 nm. This broad energy range, and specifically 800 nm, is not resonant with any phonon modes, yet induced electronic excitations appear to be connected to superconductivity at energy scales well above the typical gap energies in the cuprates. A critical question is what can be responsible for such an effect at 800 nm? Using time-dependent exact diagonalization, we demonstrate that the holes in the CuO2 plane can be photoexcited into the charge reservoir layers at resonant wavelengths within a multi-band Hubbard model. This orbitally selective photoinduced charge transfer effectively changes the in-plane doping level, which can lead to an enhancement of Tc near the 1/8 anomaly.

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“…Since our model lacks electron-phonon coupling and electron-electron scattering, their specific role in the trRIXS of the graphene nanoribbon will need to be investigated in future studies. While RIXS can observe electron-phonon coupling 38,54,55 and excitations caused by electron correlation 56 , in the case of the graphene nanoribbon it is unclear whether they will have significant contributions to the spectra 57 .…”

Section: Discussionmentioning

confidence: 99%

Observing photo-induced chiral edge states of graphene nanoribbons in pump-probe spectroscopies

et al. 2020

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Photo-induced edge states in low-dimensional materials have attracted considerable attention due to the tunability of topological properties and dispersion. Specifically, graphene nanoribbons have been predicted to host chiral edge modes upon irradiation with circularly polarized light. Here, we present numerical calculations of time-resolved angle resolved photoemission spectroscopy and trRIXS of a graphene nanoribbon. We characterize pump-probe spectroscopic signatures of photo-induced edge states, illustrate the origin of distinct spectral features that arise from Floquet topological edge modes, and investigate the roles of incoming photon energies and finite core–hole lifetime in RIXS. With momentum, energy, and time resolution, pump-probe spectroscopies can play an important role in understanding the behavior of photo-induced topological states of matter.

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Time-resolved resonant inelastic x-ray scattering in a pumped Mott insulator

Cited by 23 publications

References 89 publications

X-ray scattering from light-driven spin fluctuations in a doped Mott insulator

X-ray scattering from light-driven spin fluctuations in a doped Mott insulator

Orbitally selective resonant photodoping to enhance superconductivity

Observing photo-induced chiral edge states of graphene nanoribbons in pump-probe spectroscopies

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