| 1. |
- John Mukkattukavil, D., et al.
(författare)
-
Resonant inelastic soft x-ray scattering on LaPt 2 Si 2
- 2022
-
Ingår i: Journal of physics. Condensed matter : an Institute of Physics journal. - 1361-648X .- 0953-8984. ; 34:32
-
Tidskriftsartikel (refereegranskat)abstract
- X-ray absorption and resonant inelastic x-ray scattering spectra of LaPt2Si2single crystal at the Si 2pand La 4dedges are presented. The data are interpreted in terms of density functional theory, showing that the Si spectra can be described in terms of Sisanddlocal partial density of states (LPDOS), and the La spectra are due to quasi-atomic local 4fexcitations. Calculations show that Ptd-LPDOS dominates the occupied states, and a sharp localized Lafstate is found in the unoccupied states, in line with the observations.
|
|
| 2. |
- John Mukkattukavil, Deepak, et al.
(författare)
-
Resonant inelastic soft x-ray scattering on LaPt2Si2
- 2022
-
Ingår i: Journal of Physics. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 34:32, s. 324003-
-
Tidskriftsartikel (refereegranskat)abstract
- X-ray absorption and resonant inelastic x-ray scattering spectra of LaPt2Si2 single crystal at the Si 2p and La 4d edges are presented. The data are interpreted in terms of density functional theory, showing that the Si spectra can be described in terms of Si s and d local partial density of states (LPDOS), and the La spectra are due to quasi-atomic local 4f excitations. Calculations show that Pt d-LPDOS dominates the occupied states, and a sharp localized La f state is found in the unoccupied states, in line with the observations.
|
|
| 3. |
- Mukkattukavil, Deepak John, 1993-, et al.
(författare)
-
Resonant inelastic soft x-ray scattering on LaPt2Si2
- 2022
-
Ingår i: Journal of Physics. - : Institute of Physics Publishing (IOPP). - 0953-8984 .- 1361-648X. ; 34:32
-
Tidskriftsartikel (refereegranskat)abstract
- X-ray absorption and resonant inelastic x-ray scattering spectra of LaPt2Si2 single crystal at the Si 2p and La 4d edges are presented. The data are interpreted in terms of density functional theory, showing that the Si spectra can be described in terms of Si s and d local partial density of states (LPDOS), and the La spectra are due to quasi-atomic local 4f excitations. Calculations show that Pt d-LPDOS dominates the occupied states, and a sharp localized La f state is found in the unoccupied states, in line with the observations.
|
|
| 4. |
- von Arx, Karin, 1993, et al.
(författare)
-
Fate of charge order in overdoped La-based cuprates
- 2023
-
Ingår i: NPJ QUANTUM MATERIALS. - : Springer Nature. - 2397-4648. ; 8:1
-
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.
|
|
| 5. |
- Wang, Qisi, et al.
(författare)
-
Charge order lock-in by electron-phonon coupling in La1.675Eu0.25Sr0.125CuO4
- 2021
-
Ingår i: Science Advances. - : American Association for the Advancement of Science (AAAS). - 2375-2548. ; 7:27
-
Tidskriftsartikel (refereegranskat)abstract
- Charge order is universal to all hole-doped cuprates. Yet, the driving interactions remain an unsolved problem. Electron-electron interaction is widely believed to be essential, whereas the role of electron-phonon interaction is unclear. We report an ultrahigh-resolution resonant inelastic x-ray scattering (RIXS) study of the in-plane bondstretching phonon mode in stripe-ordered cuprate La1.675Eu0.25Sr0.125CuO4. Phonon softening and lifetime shortening are found around the charge ordering wave vector. In addition to these self-energy effects, the electron-phonon coupling is probed by its proportionality to the RIXS cross section. We find an enhancement of the electron-phonon coupling around the charge-stripe ordering wave vector upon cooling into the low-temperature tetragonal structure phase. These results suggest that, in addition to electronic correlations, electron-phonon coupling contributes substantially to the emergence of long-range charge-stripe order in cuprates.
|
|
| 6. |
- Wang, Qisi, et al.
(författare)
-
Ferromagnetic exchange interaction probed in YFe2Ge2 by resonant inelastic x-ray scattering
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- We report a combined resonant inelastic x-ray scattering and inelastic neutron scattering study of YFe2Ge2. Our data reveal that the A-type magnetic excitations are dominating over the whole energy range suggestive of a ferromagnetic fluctuation mediated p-wave Cooper pairing in this compound. As the magnetic frustration is mediated by conduction electrons which could be highly tunable, for example by doping (pressure), Our results, therefore, suggest the possibility of enhancing Tc in this system.
|
|
| 7. |
- Wang, Qisi, et al.
(författare)
-
High-Temperature Charge-Stripe Correlations in La1.675Eu0.2Sr0.125CuO4
- 2020
-
Ingår i: Physical Review Letters. - : AMER PHYSICAL SOC. - 1079-7114 .- 0031-9007. ; 124:18
-
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.
|
|
| 8. |
- Wang, Qisi, et al.
(författare)
-
Magnon interactions in a moderately correlated Mott insulator
- 2024
-
Ingår i: Nature Communications. - : Springer Nature. - 2041-1723. ; 15:1
-
Tidskriftsartikel (refereegranskat)abstract
- Quantum fluctuations in low-dimensional systems and near quantum phase transitions have significant influences on material properties. Yet, it is difficult to experimentally gauge the strength and importance of quantum fluctuations. Here we provide a resonant inelastic x-ray scattering study of magnon excitations in Mott insulating cuprates. From the thin film of SrCuO2, single- and bi-magnon dispersions are derived. Using an effective Heisenberg Hamiltonian generated from the Hubbard model, we show that the single-magnon dispersion is only described satisfactorily when including significant quantum corrections stemming from magnon-magnon interactions. Comparative results on La2CuO4 indicate that quantum fluctuations are much stronger in SrCuO2 suggesting closer proximity to a magnetic quantum critical point. Monte Carlo calculations reveal that other magnetic orders may compete with the antiferromagnetic Néel order as the ground state. Our results indicate that SrCuO2—due to strong quantum fluctuations—is a unique starting point for the exploration of novel magnetic ground states.
|
|
| 9. |
- Wang, Qisi, et al.
(författare)
-
Uniaxial pressure induced stripe order rotation in La1.88Sr0.12CuO4
- 2022
-
Ingår i: Nature Communications. - : Springer Nature. - 2041-1723. ; 13:1
-
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. Transverse stripe order fluctuations may promote superconductivity, but experimental verifications remain difficult. Here, the authors report that a mild uniaxial pressure changes the ordering pattern and pins the stripe order to the crystal axis in La1.88Sr0.12CuO4.
|
|
