| 1. |
- Kawashima, T., et al.
(författare)
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Examination of fragment ions of polystyrene in TOF-SIMS spectra using MS/MS
- 2014
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Ingår i: Surface and Interface Analysis. - : Wiley. - 0142-2421 .- 1096-9918. ; 46, s. 92-95
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Tidskriftsartikel (refereegranskat)abstract
- In this study, tendencies of ionization and cleavage processes of time-of-flight (TOF)-SIMS were examined using MS/MS, which enables an easy qualitative analysis of organic matters, to clarify the fragment ions showing structures of the organic materials. In this paper, a result of reviewing fragment ions in TOF-SIMS spectra for polystyrene (PS) as the representative material is shown. Samples were measured with collision induced dissociation (CID)-MS/MS of 1200L (Varian Inc., USA) and TOF-SIMS J105 (Ionoptika Ltd, UK) for the examination of fragment ions of the PS in TOF-SIMS spectra. The use of CID MS/MS with a wide range of energy distribution is effective for the study of the ionization and cleavage process of TOF-SIMS. As a result, the fragment ions representing the PS structure were clarified, which is useful for the material definition. The qualitative analysis was also applied to the fragment ions particularly obtained in this examination. It is suggested that the examination of the fragmentation process using MS/MS is useful for the mass spectra analysis of organic materials in TOF-SIMS. Copyright (c) 2014 John Wiley & Sons, Ltd.
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| 2. |
- Küspert, Julia, et al.
(författare)
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Pseudogap suppression by competition with superconductivity in La-based cuprates
- 2022
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Ingår i: Physical Review Research. - 2643-1564. ; 4:4
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Tidskriftsartikel (refereegranskat)abstract
- We carried out a comprehensive high-resolution angle-resolved photoemission spectroscopy (ARPES) study of the pseudogap interplay with superconductivity in La-based cuprates. The three systems La2-xSrxCuO4, La1.6-xNd0.4SrxCuO4, and La1.8-xEu0.2SrxCuO4 display slightly different pseudogap critical points in the temperature versus doping phase diagram. We studied the pseudogap evolution into the superconducting state for doping concentrations just below the critical point. In this setting, near optimal doping for superconductivity and in the presence of the weakest possible pseudogap, we uncover how the pseudogap is partially suppressed inside the superconducting state. This conclusion is based on the direct observation of a reduced pseudogap energy scale and re-emergence of spectral weight suppressed by the pseudogap. Altogether these observations suggest that the pseudogap phenomenon in La-based cuprates is in competition with superconductivity for antinodal spectral weight.
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| 3. |
- von Arx, Karin, 1993, et al.
(författare)
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Fate of charge order in overdoped La-based cuprates
- 2023
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Ingår i: NPJ QUANTUM MATERIALS. - : Springer Nature. - 2397-4648. ; 8:1
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Tidskriftsartikel (refereegranskat)abstract
- In high-temperature cuprate superconductors, stripe order refers broadly to a coupled spin and charge modulation with a commensuration of eight and four lattice units, respectively. How this stripe order evolves across optimal doping remains a controversial question. Here we present a systematic resonant inelastic x-ray scattering study of weak charge correlations in La2-xSrxCuO4 and La1.8-xEu0.2SrxCuO4. Ultra high energy resolution experiments demonstrate the importance of the separation of inelastic and elastic scattering processes. Long-range temperature-dependent stripe order is only found below optimal doping. At higher doping, short-range temperature-independent correlations are present up to the highest doping measured. This transformation is distinct from and preempts the pseudogap critical doping. We argue that the doping and temperature-independent short-range correlations originate from unresolved electron-phonon coupling that broadly peaks at the stripe ordering vector. In La2-xSrxCuO4, long-range static stripe order vanishes around optimal doping and we discuss both quantum critical and crossover scenarios.
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| 4. |
- Wang, Qisi, et al.
(författare)
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High-Temperature Charge-Stripe Correlations in La1.675Eu0.2Sr0.125CuO4
- 2020
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Ingår i: Physical Review Letters. - : AMER PHYSICAL SOC. - 1079-7114 .- 0031-9007. ; 124:18
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Tidskriftsartikel (refereegranskat)abstract
- We use resonant inelastic x-ray scattering to investigate charge-stripe correlations in La1.675Eu0.2Sr0.125CuO4. By differentiating elastic from inelastic scattering, it is demonstrated that charge-stripe correlations precede both the structural low-temperature tetragonal phase and the transport-defined pseudogap onset. The scattering peak amplitude from charge stripes decays approximately as T-2 towards our detection limit. The in-plane integrated intensity, however, remains roughly temperature independent. Therefore, although the incommensurability shows a remarkably large increase at high temperature, our results are interpreted via a single scattering constituent. In fact, direct comparison to other stripe-ordered compounds (La1.875Ba0.125CuO4, La1.475Nd0.4Sr0.125CuO4, and La1.875Sr0.125CuO4) suggests a roughly constant integrated scattering intensity across all these compounds. Our results therefore provide a unifying picture for the charge-stripe ordering in La-based cuprates. As charge correlations in La1.675Eu0.2Sr0.125CuO4 extend beyond the low-temperature tetragonal and pseudogap phase, their emergence heralds a spontaneous symmetry breaking in this compound.
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| 5. |
- Wang, Q., et al.
(författare)
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Uniaxial pressure induced stripe order rotation in La 1.88 Sr 0.12 CuO 4
- 2022
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723 .- 2041-1723. ; 13:1
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Tidskriftsartikel (refereegranskat)abstract
- Static stripe order is detrimental to superconductivity. Yet, it has been proposed that transverse stripe fluctuations may enhance the inter-stripe Josephson coupling and thus promote superconductivity. Direct experimental studies of stripe dynamics, however, remain difficult. From a strong-coupling perspective, transverse stripe fluctuations are realized in the form of dynamic “kinks”—sideways shifting stripe sections. Here, we show how modest uniaxial pressure tuning reorganizes directional kink alignment. Our starting point is La1.88Sr0.12CuO4 where transverse kink ordering results in a rotation of stripe order away from the crystal axis. Application of mild uniaxial pressure changes the ordering pattern and pins the stripe order to the crystal axis. This reordering occurs at a much weaker pressure than that to detwin the stripe domains and suggests a rather weak transverse stripe stiffness. Weak spatial stiffness and transverse quantum fluctuations are likely key prerequisites for stripes to coexist with superconductivity.
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