Angstrom-Resolved Interfacial Structure in Buried Organic-Inorganic Junctions

Schwartz, Craig P.; Raj, Sumana L.; Jamnuch, Sasawat; Hull, Chris J.; Miotti, Paolo; Lam, Royce K.; Nordlund, Dennis; Uzundal, Can Berk; Pemmaraju, C. D.; Mincigrucci, Riccardo; Foglia, Laura; Simoncig, Alberto; Coreno, Marcello; Masciovecchio, C.; Giannessi, L.; Poletto, Luca; Principi, Emiliano; Zuerch, Michael; Pascal, Tod A.; Drisdell, Walter S.; Saykally, R. J.

doi:10.1103/physrevlett.127.096801

Cited by 16 publications

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“…The χ eff (2) spectrum was then extracted using eq after binning and averaging spectra based on the photon energy and intensity of the driving fundamental pulse. The inherent jitter of the XFEL, both in frequency and intensity, allowed for a high-fidelity extraction of χ eff (2) ( 2ω) with significantly more data points, compared to refs − . For the T = 62 K set of measurements, a quadratic function was fit to a plot of I (ω) vs I (2ω), at each energy where the second-order fit coefficient is modulo |χ eff (2) (2ω)| 2 , with χ eff (2) (2ω) a rank-three tensor of four independent components (χ zzz (2) ,χ xxz (2) , χ zxx (2) , and χ xxy (2) ), because of point group symmetry (Figure e).…”

Section: Resultsmentioning

confidence: 99%

“…Given the orbital character of states around the Fermi surface, it is not surprising then that an order-of-magnitude weaker optical SHG signal was found in LiOsO 3 , compared to LiTaO 3 and LiNbO 3 . 20 To gain insight into the nature of the polar phase, we turn to extreme ultraviolet second harmonic generation (XUV-SHG) spectroscopy, which is a newly developed method viable for studying bulk-phase noncentrosymmetric masterials, 21 surfaces, 22,23 and buried interfaces 24 in the XUV or the soft X-ray (SXR) regimes, where the objective is to perform SHG under resonant conditions, and in the hard X-ray regime, where a nonresonant approach is usually taken. 25−27 In SXR-or XUV-SHG spectroscopy, the incident X-ray beam is resonant or halfresonant with a core-to-valence transition, such that the resulting resonantly enhanced, background-free signal is sensitive to core levels in the electronic structure.…”

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confidence: 99%

“…To gain insight into the nature of the polar phase, we turn to extreme ultraviolet second harmonic generation (XUV-SHG) spectroscopy, which is a newly developed method viable for studying bulk-phase noncentrosymmetric masterials, surfaces, , and buried interfaces in the XUV or the soft X-ray (SXR) regimes, where the objective is to perform SHG under resonant conditions, and in the hard X-ray regime, where a nonresonant approach is usually taken. − In SXR- or XUV-SHG spectroscopy, the incident X-ray beam is resonant or half-resonant with a core-to-valence transition, such that the resulting resonantly enhanced, background-free signal is sensitive to core levels in the electronic structure. By energetically resolving the SHG emission, the symmetry breaking can be correlated to particular spectral features.…”

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confidence: 99%

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Extreme Ultraviolet Second Harmonic Generation Spectroscopy in a Polar Metal

et al. 2021

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The coexistence of ferroelectricity and metallicity seems paradoxical, since the itinerant electrons in metals should screen the long-range dipole interactions necessary for dipole ordering. The recent discovery of the polar metal LiOsO 3 was therefore surprising [as discussed earlier in Y. Shi et al., Nat. Mater . 2013 , 12 , 1024]. It is thought that the coordination preferences of the Li play a key role in stabilizing the LiOsO 3 polar metal phase, but an investigation from the combined viewpoints of core-state specificity and symmetry has yet to be done. Here, we apply the novel technique of extreme ultraviolet second harmonic generation (XUV-SHG) and find a sensitivity to the broken inversion symmetry in the polar metal phase of LiOsO 3 with an enhanced feature above the Li K-edge that reflects the degree of Li atom displacement as corroborated by density functional theory calculations. These results pave the way for time-resolved probing of symmetry-breaking structural phase transitions on femtosecond time scales with element specificity.

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Extreme Ultraviolet Second Harmonic Generation Spectroscopy in a Polar Metal

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“…In contrast, four-wave mixing (FWM), as a third-order nonlinear process, is able to address the bulk properties of any material, irrespective of its symmetry. Here, first experimental investigations based on transient gratings induced by XUV FEL pulses and probed either by optical or even XUV laser pulses have been reported (7)(8)(9)(10)(11)(12). Very recently, FWM in NaCl at the Na + L 2,3 edge near 33.5 eV, using laser-generated attosecond XUV and near-infrared (NIR) laser pulses, revealed the presence of dark excited states, i.e., states not dipole coupled to the electronic ground state of the material (13).…”

Section: Introductionmentioning

confidence: 99%

Probing electron and hole colocalization by resonant four-wave mixing spectroscopy in the extreme ultraviolet

et al. 2022

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Extending nonlinear spectroscopic techniques into the x-ray domain promises unique insight into photoexcited charge dynamics, which are of fundamental and applied interest. We report on the observation of a third-order nonlinear process in lithium fluoride (LiF) at a free-electron laser. Exploring the yield of four-wave mixing (FWM) in resonance with transitions to strongly localized core exciton states versus delocalized Bloch states, we find resonant FWM to be a sensitive probe for the degree of charge localization: Substantial sum- and difference-frequency generation is observed exclusively when in a one- or three-photon resonance with a LiF core exciton, with a dipole forbidden transition affecting details of the nonlinear response. Our reflective geometry–based approach to detect FWM signals enables the study of a wide variety of condensed matter sample systems, provides atomic selectivity via resonant transitions, and can be easily scaled to shorter wavelengths at free-electron x-ray lasers.

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“…x-ray optics phenomena [4,5,[35][36][37]. This opens up new opportunities to track, understand, and control electronic processes in molecules [38][39][40][41][42].…”

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Femtosecond-Terawatt Hard X Ray Pulse Generation with Chirped Pulse Amplification on a Free Electron Laser

Li¹,

Littleton²,

Dunne³

et al. 2022

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Advances of high intensity lasers have opened up the field of strong field physics and led to a broad range of technological applications. Recent x ray laser sources and optics development makes it possible to obtain extremely high intensity and brightness at x ray wavelengths. In this paper, we present a system design that implements chirped pulse amplification for hard x ray free electron lasers. Numerical modeling with realistic experimental parameters show that near-transform-limit single-femtosecond hard x ray laser pulses with peak power exceeding 1 TW and brightness exceeding 4 × 10 35 s −1 mm −2 mrad −2 0.1%bandwdith −1 can be consistently generated. Realization of such beam qualities is essential for establishing systematic and quantitative understanding of strong field x-ray physics and nonlinear x ray optics phenomena.High-intensity high-brightness x-ray pulses from free electron laser (FEL) have opened up many new routes of research for strong field physics [1, 2], non-linear x-ray optics, and many potential applications [3][4][5][6][7][8][9][10][11][12]. While the past decade have witnessed many first demonstrations, one major obstacle towards a quantitative, systematic and application-oriented understanding of the subject came from the stochastic temporal and spectral structure of the pulses [13]. Production of Terawatt-femtosecond (TW-fs) hard x ray pulses with full spatial and temporal coherence is therefore highly desired. This calls for allround-improvement of the x ray beam quality, including peak intensity, peak brightness, and a well defined spatial temporal profile, which are mandatory for quantitative analysis and prediction of the nonlinear observables.Currently, the peak power of a state-of-art free electron laser (FEL) can reach 100 GW scale [14] through self-amplified spontaneous emission (SASE). To push the peak power into TW scale, several enhanced-SASE schemes [15][16][17] have projected terawatt-attosecond (TWas) output by using extremely high peak current. A super-radiance based approach [18] was shown to be capable of delivering TW hard x-ray pulses with a sequence of short electron bunches and electron and optical delay devices. These approaches still inherited the rugged temporal characteristics of SASE, while also requiring electron beam parameters beyond the current state-of-art. Self-seeding techniques were adopted to improve the temporal coherence up on SASE [19][20][21][22] with impressive peak brightness improvement. However,

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Angstrom-Resolved Interfacial Structure in Buried Organic-Inorganic Junctions

Cited by 16 publications

References 48 publications

Extreme Ultraviolet Second Harmonic Generation Spectroscopy in a Polar Metal

Extreme Ultraviolet Second Harmonic Generation Spectroscopy in a Polar Metal

Probing electron and hole colocalization by resonant four-wave mixing spectroscopy in the extreme ultraviolet

Femtosecond-Terawatt Hard X Ray Pulse Generation with Chirped Pulse Amplification on a Free Electron Laser

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