I21-Resonant Inelastic X-ray Scattering (RIXS)
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Open Access
Abstract: Upon progressive refinement of energy resolution, the conventional resonant inelastic X-ray scattering (RIXS) instrumentation reaches the limit where the bandwidth of incident photons becomes insufficient to deliver an acceptable photon-count rate. Here it is shown that RIXS spectra as a function of energy loss are essentially invariant to their integration over incident energies within the core-hole lifetime. This fact permits RIXS instrumentation based on the hv2-concept to utilize incident synchrotron radiation over the whole core-hole lifetime window without any compromise on the much finer energy-loss resolution, thereby breaking the photon-count limit.
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Sep 2020
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I21-Resonant Inelastic X-ray Scattering (RIXS)
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Diamond Proposal Number(s):
[23889]
Abstract: Li-rich cathode materials are potential candidates for next-generation Li-ion batteries. However, they exhibit a large voltage hysteresis on the first charge/discharge cycle, which involves a substantial (up to 1 V) loss of voltage and therefore energy density. For Na cathodes, for example Na0.75[Li0.25Mn0.75]O2, voltage hysteresis can be explained by the formation of molecular O2 trapped in voids within the particles. Here we show that this is also the case for Li1.2Ni0.13Co0.13Mn0.54O2. Resonant inelastic X-ray scattering and 17O magic angle spinning NMR spectroscopy show that molecular O2, rather than O22−, forms within the particles on the oxidation of O2− at 4.6 V versus Li+/Li on charge. These O2 molecules are reduced back to O2− on discharge, but at the lower voltage of 3.75 V, which explains the voltage hysteresis in Li-rich cathodes. 17O magic angle spinning NMR spectroscopy indicates a quantity of bulk O2 consistent with the O-redox charge capacity minus the small quantity of O2 loss from the surface. The implication is that O2, trapped in the bulk and lost from the surface, can explain O-redox.
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Sep 2020
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I21-Resonant Inelastic X-ray Scattering (RIXS)
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W. S.
Lee
,
K.
Zhou
,
M.
Hepting
,
J.
Li
,
A.
Nag
,
A. C.
Walters
,
M.
Garcia-fernandez
,
H. C.
Robarts
,
M.
Hashimoto
,
H.
Lu
,
B.
Nosarzewski
,
D.
Song
,
H.
Eisaki
,
Z. X.
Shen
,
B.
Moritz
,
J.
Zaanen
,
T. P.
Devereaux
Diamond Proposal Number(s):
[18462]
Abstract: Copper oxide high-TC superconductors possess a number of exotic orders that coexist with or are proximal to superconductivity. Quantum fluctuations associated with these orders may account for the unusual characteristics of the normal state, and possibly affect the superconductivity1,2,3,4. Yet, spectroscopic evidence for such quantum fluctuations remains elusive. Here, we use resonant inelastic X-ray scattering to reveal spectroscopic evidence of fluctuations associated with a charge order5,6,7,8,9,10,11,12,13,14 in nearly optimally doped Bi2Sr2CaCu2O8+δ. In the superconducting state, while the quasielastic charge order signal decreases with temperature, the interplay between charge order fluctuations and bond-stretching phonons in the form of a Fano-like interference increases, an observation that is incompatible with expectations for competing orders. Invoking general principles, we argue that this behaviour reflects the properties of a dissipative system near an order–disorder quantum critical point, where the dissipation varies with the opening of the pseudogap and superconducting gap at low temperatures, leading to the proliferation of quantum critical fluctuations, which melt charge order.
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Aug 2020
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I21-Resonant Inelastic X-ray Scattering (RIXS)
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Soonmin
Kang
,
Kangwon
Kim
,
Beom Hyun
Kim
,
Jonghyeon
Kim
,
Kyung Ik
Sim
,
Jae-ung
Lee
,
Sungmin
Lee
,
Kisoo
Park
,
Seokhwan
Yun
,
Taehun
Kim
,
Abhishek
Nag
,
Andrew
Walters
,
Mirian
Garcia-fernandez
,
Jiemin
Li
,
Laurent
Chapon
,
Kejin
Zhou
,
Young-woo
Son
,
Jae Hoon
Kim
,
Hyeonsik
Cheong
,
Je-geun
Park
Diamond Proposal Number(s):
[18503, 18906]
Abstract: An exciton is the bosonic quasiparticle of electron–hole pairs bound by the Coulomb interaction. Bose–Einstein condensation of this exciton state has long been the subject of speculation in various model systems and examples have been found more recently in optical lattices and two-dimensional materials. Unlike these conventional excitons formed from extended Bloch states, excitonic bound states from intrinsically many-body localized states are rare. Here we show that a spin–orbit-entangled exciton state appears below the Néel temperature of 150 kelvin in NiPS3, an antiferromagnetic van der Waals material. It arises intrinsically from the archetypal many-body states of the Zhang–Rice singlet, and reaches a coherent state assisted by the antiferromagnetic order. Using configuration-interaction theory, we determine the origin of the coherent excitonic excitation to be a transition from a Zhang–Rice triplet to a Zhang–Rice singlet. We combine three spectroscopic tools—resonant inelastic X-ray scattering, photoluminescence and optical absorption—to characterize the exciton and to demonstrate an extremely narrow excitonic linewidth below 50 kelvin. The discovery of the spin–orbit-entangled exciton in antiferromagnetic NiPS3 introduces van der Waals magnets as a platform to study coherent many-body excitons.
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Jul 2020
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I21-Resonant Inelastic X-ray Scattering (RIXS)
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Jiemin
Li
,
Abhishek
Nag
,
Jonathan
Pelliciari
,
Hannah
Robarts
,
Andrew
Walters
,
Mirian
Garcia-fernandez
,
Hiroshi
Eisaki
,
Dongjoon
Song
,
Hong
Ding
,
Steven
Johnston
,
Riccardo
Comin
,
Kejin
Zhou
Diamond Proposal Number(s):
[19886, 21184, 21277]
Open Access
Abstract: Charge-density waves (CDWs) are ubiquitous in underdoped cuprate superconductors. As a modulation of the valence electron density, CDWs in hole-doped cuprates possess both Cu-3d and O-2p orbital character owing to the strong hybridization of these orbitals near the Fermi level. Here, we investigate underdoped Bi2Sr1.4La0.6CuO6+δ using resonant inelastic X-ray scattering (RIXS) and find that a short-range CDW exists at both Cu and O sublattices in the copper-oxide (CuO2) planes with a comparable periodicity and correlation length. Furthermore, we uncover bond-stretching and bond-buckling phonon anomalies concomitant to the CDWs. Comparing to slightly overdoped Bi2Sr1.8La0.2CuO6+δ, where neither CDWs nor phonon anomalies appear, we highlight that a sharp intensity anomaly is induced in the proximity of the CDW wavevector (QCDW) for the bond-buckling phonon, in concert with the diffused intensity enhancement of the bond-stretching phonon at wavevectors much greater than QCDW. Our results provide a comprehensive picture of the quasistatic CDWs, their dispersive excitations, and associated electron-phonon anomalies, which are key for understanding the competing electronic instabilities in cuprates.
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Jun 2020
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I21-Resonant Inelastic X-ray Scattering (RIXS)
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J. Q.
Lin
,
H.
Miao
,
D. G.
Mazzone
,
G. D.
Gu
,
A.
Nag
,
A. C.
Walters
,
M.
Garcia-fernandez
,
A.
Barbour
,
J.
Pelliciari
,
I.
Jarrige
,
M.
Oda
,
K.
Kurosawa
,
N.
Momono
,
K.
Zhou
,
V.
Bisogni
,
X.
Liu
,
M. P. M.
Dean
Diamond Proposal Number(s):
[22261]
Abstract: The discovery of charge-density-wave-related effects in the resonant inelastic x-ray scattering spectra of cuprates holds the tantalizing promise of clarifying the interactions that stabilize the electronic order. Here, we report a comprehensive resonant inelastic x-ray scattering study of
La
2
−
x
Sr
x
CuO
4
finding that charge-density wave effects persist up to a remarkably high doping level of
x
=
0.21
before disappearing at
x
=
0.25
. The inelastic excitation spectra remain essentially unchanged with doping despite crossing a topological transition in the Fermi surface. This indicates that the spectra contain little or no direct coupling to electronic excitations near the Fermi surface, rather they are dominated by the resonant cross section for phonons and charge-density-wave-induced phonon softening. We interpret our results in terms of a charge-density wave that is generated by strong correlations and a phonon response that is driven by the charge-density-wave-induced modification of the lattice.
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May 2020
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I21-Resonant Inelastic X-ray Scattering (RIXS)
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Q.
Wang
,
M.
Horio
,
K.
Von Arx
,
Y.
Shen
,
D.
John Mukkattukavil
,
Y.
Sassa
,
O.
Ivashko
,
C. E.
Matt
,
S.
Pyon
,
T.
Takayama
,
H.
Takagi
,
T.
Kurosawa
,
N.
Momono
,
M.
Oda
,
T.
Adachi
,
S. M.
Haidar
,
Y.
Koike
,
Y.
Tseng
,
W.
Zhang
,
J.
Zhao
,
K.
Kummer
,
M.
Garcia-fernandez
,
K.
Zhou
,
N. B.
Christensen
,
H. M.
Ronnow
,
T.
Schmitt
,
J.
Chang
Diamond Proposal Number(s):
[20828, 24481]
Abstract: We use resonant inelastic x-ray scattering to investigate charge-stripe correlations in
La
1.675
Eu
0.2
Sr
0.125
CuO
4
. 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 (
La
1.875
Ba
0.125
CuO
4
,
La
1.475
Nd
0.4
Sr
0.125
CuO
4
, and
La
1.875
Sr
0.125
CuO
4
) 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
La
1.675
Eu
0.2
Sr
0.125
CuO
4
extend beyond the low-temperature tetragonal and pseudogap phase, their emergence heralds a spontaneous symmetry breaking in this compound.
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May 2020
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I21-Resonant Inelastic X-ray Scattering (RIXS)
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A.
Nag
,
H. C.
Robarts
,
F.
Wenzel
,
J.
Li
,
H.
Elnaggar
,
R.-p.
Wang
,
A.
Walters
,
M.
Garcia-fernandez
,
F. M. F.
De Groot
,
M. W.
Haverkort
,
K.
Zhou
Open Access
Abstract: Understanding many-body physics of elementary excitations has advanced our control over material properties. Here, we study spin-flip excitations in NiO using Ni
L3-edge resonant inelastic x-ray scattering (RIXS) and present a strikingly different resonant energy behavior between single and double spin-flip excitations. Comparing our results with single-site full-multiplet ligand field theory calculations we find that the spectral weight of the double-magnon excitations originates primarily from the double spin-flip transition of the quadrupolar RIXS process within a single magnetic site. Quadrupolar spin-flip processes are among the least studied excitations, despite being important for multiferroic or spin-nematic materials due to their difficult detection. We identify intermediate state multiplets and intra-atomic core-valence exchange interactions as the key many-body factors determining the fate of such excitations. RIXS resonant energy dependence can act as a convincing proof of existence of nondipolar higher-ranked magnetic orders in systems for which, only theoretical predictions are available.
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Feb 2020
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I21-Resonant Inelastic X-ray Scattering (RIXS)
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M.
Hepting
,
D.
Li
,
C. J.
Jia
,
H.
Lu
,
E.
Paris
,
Y.
Tseng
,
X.
Feng
,
M.
Osada
,
E.
Been
,
Y.
Hikita
,
Y.-d.
Chuang
,
Z.
Hussain
,
K. J.
Zhou
,
A.
Nag
,
M.
Garcia-fernandez
,
M.
Rossi
,
H. Y.
Huang
,
D. J.
Huang
,
Z. X.
Shen
,
T.
Schmitt
,
H. Y.
Hwang
,
B.
Moritz
,
J.
Zaanen
,
T. P.
Devereaux
,
W. S.
Lee
Diamond Proposal Number(s):
[22009]
Abstract: The search continues for nickel oxide-based materials with electronic properties similar to cuprate high-temperature superconductors. The recent discovery of superconductivity in the doped infinite-layer nickelate NdNiO2 has strengthened these efforts. Here, we use X-ray spectroscopy and density functional theory to show that the electronic structure of LaNiO2 and NdNiO2, while similar to the cuprates, includes significant distinctions. Unlike cuprates, the rare-earth spacer layer in the infinite-layer nickelate supports a weakly interacting three-dimensional 5d metallic state, which hybridizes with a quasi-two-dimensional, strongly correlated state with
3
d
x
2
−
y
2
3dx2−y2
symmetry in the NiO2 layers. Thus, the infinite-layer nickelate can be regarded as a sibling of the rare-earth intermetallics, which are well known for heavy fermion behaviour, where the NiO2 correlated layers play an analogous role to the 4f states in rare-earth heavy fermion compounds. This Kondo- or Anderson-lattice-like ‘oxide-intermetallic’ replaces the Mott insulator as the reference state from which superconductivity emerges upon doping.
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Jan 2020
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I21-Resonant Inelastic X-ray Scattering (RIXS)
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Jiaqi
Lin
,
Jie
Yuan
,
Kui
Jin
,
Zhiping
Yin
,
Gang
Li
,
Kejin
Zhou
,
Xingye
Lu
,
Marcus
Dantz
,
Thorsten
Schmitt
,
Hong
Ding
,
Haizhong
Guo
,
Mark P. M.
Dean
,
Xuerong
Liu
Open Access
Abstract: Electron correlations play a dominant role in the charge dynamics of the cuprates. We use resonant inelastic X-ray scattering (RIXS) to track the doping dependence of the collective charge excitations in electron doped La
2−x
2−x
Ce
x
x
CuO
4
4
(LCCO). From the resonant energy dependence and the out-of-plane momentum dependence, the charge excitations are identified as three-dimensional (3D) plasmons, which reflect the nature of the electronic structure and Coulomb repulsion on both short and long lengthscales. With increasing electron doping, the plasmon excitations increase monotonically in energy, a consequence of the electron correlation effect on electron structure near the Fermi surface (FS). Importantly, the plasmon excitations evolve from a broad feature into a well-defined peak with much increased life time, revealing the evolution of the electrons from incoherent states to coherent quasi-particles near the FS. Such evolution marks the reduction of the short-range electronic correlation, and thus the softening of the Mottness of the system with increasing electron doping.
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Jan 2020
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