I21-Resonant Inelastic X-ray Scattering (RIXS)
|
Xiang
Ding
,
Charles C.
Tam
,
Xuelei
Sui
,
Yan
Zhao
,
Minghui
Xu
,
Jaewon
Choi
,
Huaqian
Leng
,
Ji
Zhang
,
Mei
Wu
,
Haiyan
Xiao
,
Xiaotao
Zu
,
Mirian
Garcia-Fernandez
,
Stefano
Agrestini
,
Xiaoqiang
Wu
,
Qingyuan
Wang
,
Peng
Gao
,
Sean
Li
,
Bing
Huang
,
Ke-Jin
Zhou
,
Liang
Qiao
Diamond Proposal Number(s):
[30296]
Abstract: The newly discovered nickelate superconductors so far only exist in epitaxial thin films synthesized by a topotactic reaction with metal hydrides1. This method changes the nickelates from the perovskite to an infinite-layer structure by deintercalation of apical oxygens1,2,3. Such a chemical reaction may introduce hydrogen (H), influencing the physical properties of the end materials4,5,6,7,8,9. Unfortunately, H is insensitive to most characterization techniques and is difficult to detect because of its light weight. Here, in optimally Sr doped Nd0.8Sr0.2NiO2H epitaxial films, secondary-ion mass spectroscopy shows abundant H existing in the form of Nd0.8Sr0.2NiO2Hx (x ≅ 0.2–0.5). Zero resistivity is found within a very narrow H-doping window of 0.22 ≤ x ≤ 0.28, showing unequivocally the critical role of H in superconductivity. Resonant inelastic X-ray scattering demonstrates the existence of itinerant interstitial s (IIS) orbitals originating from apical oxygen deintercalation. Density functional theory calculations show that electronegative H– occupies the apical oxygen sites annihilating IIS orbitals, reducing the IIS–Ni 3d orbital hybridization. This leads the electronic structure of H-doped Nd0.8Sr0.2NiO2Hx to be more two-dimensional-like, which might be relevant for the observed superconductivity. We highlight that H is an important ingredient for superconductivity in epitaxial infinite-layer nickelates.
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Mar 2023
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I09-Surface and Interface Structural Analysis
I21-Resonant Inelastic X-ray Scattering (RIXS)
|
A. S.
Menon
,
B. J.
Johnston
,
S. G.
Booth
,
L.
Zhang
,
K.
Kress
,
B. E.
Murdock
,
G.
Paez Fajardo
,
N. N.
Anthonisamy
,
N.
Tapia-Ruiz
,
S.
Agrestini
,
M.
Garcia-Fernandez
,
K.
Zhou
,
P. K.
Thakur
,
T. L.
Lee
,
A. J.
Nedoma
,
S. A.
Cussen
,
L. F. J.
Piper
Diamond Proposal Number(s):
[29104, 29113]
Open Access
Abstract: The desire to increase the energy density of stoichiometric layered
Li
TM
O
2
(TM = 3d transition metal) cathode materials has promoted investigation into their properties at high states of charge. Although there is increasing evidence for pronounced oxygen participation in the charge compensation mechanism, questions remain whether this is true
O
-redox, as observed in
Li
-excess cathodes. Through a high-resolution
O
K-edge resonant inelastic x-ray spectroscopy (RIXS) study of the
Mn
-free
Ni
-rich layered oxide
Li
Ni
0.98
W
0.02
O
2
, we demonstrate that the same oxidized oxygen environment exists in both
Li
-excess and non-
Li
-excess systems. The observation of identical RIXS loss features in both classes of compounds is remarkable given the differences in their crystallographic structure and delithiation pathways. This lack of a specific structural motif reveals the importance of electron correlation in the charge compensation mechanism for these systems and indicates how a better description of charge compensation in layered oxides is required to understand anionic redox for energy storage.
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Mar 2023
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I21-Resonant Inelastic X-ray Scattering (RIXS)
|
Eleanor
Lawrence Bright
,
Lei
Xu
,
Lottie
Harding
,
Ross
Springell
,
Andrew
Walters
,
Martin
Sundermann
,
Mirian
Garcia-Fernandez
,
Stefano
Agrestini
,
Roberto
Caciuffo
,
Gerrit
Van Der Laan
,
Gerry H.
Lander
Diamond Proposal Number(s):
[29274]
Abstract: Resonant inelastic x-ray scattering (RIXS) using an incident energy tuned to the uranium N4,5 absorption edges is reported from epitaxial films of α-U3O8 and UN. Theory shows that for U3O8 the multiplets associated with a 5f1 configuration with a ground state of 2F5/2 and the excited state of 2F7/2 are observed. However, the strong transition predicted at a transfer energy of 1.67 eV is not observed. We assume this is a consequence of the intermediate state lifetime broadening due to interaction with continuum states when the transferred energy exceeds the onset of the continuum in the presence of the core hole. This hypothesis is supported by the results obtained for the 5f-itinerant system UN, where no sharp transitions have been observed, although the broad scattering response centered at ∼ 1 eV is considered a signature of a predominantly 5f3 configuration in this band-like semi-metallic system. These experiments and theory add important information on these materials, both of which have been investigated since the 1960s, as well as whether RIXS at the uranium N edge can become a valuable tool for actinide research.
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Feb 2023
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I21-Resonant Inelastic X-ray Scattering (RIXS)
|
Abhishek
Nag
,
Yiran
Peng
,
Jiemin
Li
,
Stefano
Agrestini
,
Hannah C.
Robarts
,
Mirian
Garcia-Fernandez
,
Andrew C.
Walters
,
Qi
Wang
,
Qiangwei
Yin
,
Hechang
Lei
,
Zhiping
Yin
,
Ke-Jin
Zhou
Diamond Proposal Number(s):
[27905]
Open Access
Abstract: Among condensed matter systems, Mott insulators exhibit diverse properties that emerge from electronic correlations. In itinerant metals, correlations are usually weak, but can also be enhanced via geometrical confinement of electrons, that manifest as ‘flat’ dispersionless electronic bands. In the fast developing field of topological materials, which includes Dirac and Weyl semimetals, flat bands are one of the important components that can result in unusual magnetic and transport behaviour. To date, characterisation of flat bands and their magnetism is scarce, hindering the design of novel materials. Here, we investigate the ferromagnetic Kagomé semimetal Co3Sn2S2 using resonant inelastic X-ray scattering. Remarkably, nearly non-dispersive Stoner spin excitation peaks are observed, sharply contrasting with the featureless Stoner continuum expected in conventional ferromagnetic metals. Our band structure and dynamic spin susceptibility calculations, and thermal evolution of the excitations, confirm the nearly non-dispersive Stoner excitations as unique signatures of correlations and spin-polarized electronic flat bands in Co3Sn2S2. These observations serve as a cornerstone for further exploration of band-induced symmetry-breaking orders in topological materials.
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Nov 2022
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I21-Resonant Inelastic X-ray Scattering (RIXS)
|
Charles C.
Tam
,
Jaewon
Choi
,
Xiang
Ding
,
Stefano
Agrestini
,
Abhishek
Nag
,
Mei
Wu
,
Bing
Huang
,
Huiqian
Luo
,
Peng
Gao
,
Mirian
Garcia-Fernandez
,
Liang
Qiao
,
Ke-Jin
Zhou
Diamond Proposal Number(s):
[30296]
Abstract: In materials science, much effort has been devoted to the reproduction of superconductivity in chemical compositions, analogous to cuprate superconductors since their discovery over 30 years ago. This approach was recently successful in realising superconductivity in infinite-layer nickelates1,2,3,4,5,6. Although differing from cuprates in electronic and magnetic properties, strong Coulomb interactions suggest that infinite-layer nickelates have a propensity towards various symmetry-breaking orders that populate cuprates7,8,9,10. Here we report the observation of charge density waves (CDWs) in infinite-layer NdNiO2 films using Ni L3 resonant X-ray scattering. Remarkably, CDWs form in Nd 5d and Ni 3d orbitals at the same commensurate wavevector (0.333, 0) reciprocal lattice units, with non-negligible out-of-plane dependence and an in-plane correlation length of up to ~60 Å. Spectroscopic studies reveal a strong connection between CDWs and Nd 5d–Ni 3d orbital hybridization. Upon entering the superconducting state at 20% Sr doping, the CDWs disappear. Our work demonstrates the existence of CDWs in infinite-layer nickelates with a multiorbital character distinct from cuprates, which establishes their low-energy physics.
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Aug 2022
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I21-Resonant Inelastic X-ray Scattering (RIXS)
|
M.
Hepting
,
M.
Bejas
,
A.
Nag
,
H.
Yamase
,
N.
Coppola
,
D.
Betto
,
C.
Falter
,
Mirian
Garcia-Fernandez
,
S.
Agrestini
,
K.-J.
Zhou
,
M.
Minola
,
C.
Sacco
,
L.
Maritato
,
P.
Orgiani
,
H. I.
Wei
,
K. M.
Shen
,
D. G.
Schlom
,
A.
Galdi
,
A.
Greco
,
B.
Keimer
Diamond Proposal Number(s):
[23933]
Open Access
Abstract: We use resonant inelastic x-ray scattering to probe the propagation of plasmons in the electron-doped cuprate superconductor
Sr
0.9
La
0.1
CuO
2
. We detect a plasmon gap of
∼
120
meV
at the two-dimensional Brillouin zone center, indicating that low-energy plasmons in
Sr
0.9
La
0.1
CuO
2
are not strictly acoustic. The plasmon dispersion, including the gap, is accurately captured by layered
t
−
J
−
V
model calculations. A similar analysis performed on recent resonant inelastic x-ray scattering data from other cuprates suggests that the plasmon gap is generic and its size is related to the magnitude of the interlayer hopping
t
z
. Our work signifies the three dimensionality of the charge dynamics in layered cuprates and provides a new method to determine
t
z
.
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Jul 2022
|
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I21-Resonant Inelastic X-ray Scattering (RIXS)
|
Matteo
Rossi
,
Motoki
Osada
,
Jaewon
Choi
,
Stefano
Agrestini
,
Daniel
Jost
,
Yonghun
Lee
,
Haiyu
Lu
,
Bai Yang
Wang
,
Kyuho
Lee
,
Abhishek
Nag
,
Yi-De
Chuang
,
Cheng-Tai
Kuo
,
Sang-Jun
Lee
,
Brian
Moritz
,
Thomas P.
Devereaux
,
Zhi-Xun
Shen
,
Jun-Sik
Lee
,
Ke-Jin
Zhou
,
Harold Y.
Hwang
,
Wei-Sheng
Lee
Diamond Proposal Number(s):
[25598, 27558]
Abstract: A defining signature of strongly correlated electronic systems is a rich phase diagram, which consists of multiple broken symmetries, such as magnetism, superconductivity and charge order1,2. In the recently discovered nickelate superconductors3,4,5,6,7,8,9,10, a large antiferromagnetic exchange energy has been reported, which implies the existence of strong electronic correlations11. However, signatures of a broken-symmetry state other than superconductivity have not yet been observed. Here we observe charge ordering in infinite-layer nickelates La1−xSrxNiO2 using resonant X-ray scattering. The parent compound orders along the Ni–O bond direction with an incommensurate wavevector, distinct from the stripe order observed in other nickelates12,13,14 that propagates along a direction 45° to the Ni–O bond. The resonance profile we measure indicates that ordering originates from the nickelate layers and induces a parasitic charge modulation of lanthanum electrons. Upon doping, the charge order diminishes and its wavevector shifts towards commensurate, hinting that strong electronic correlations are likely to be responsible for the ordered state. Our results suggest that the existence of charge order and its potential interplay with antiferromagnetic fluctuations and superconductivity are important themes in nickel-based superconductors.
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Jul 2022
|
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I21-Resonant Inelastic X-ray Scattering (RIXS)
|
Diamond Proposal Number(s):
[24593]
Open Access
Abstract: The microscopic origins of emergent behaviours in condensed matter systems are encoded in their excitations. In ordinary magnetic materials, single spin-flips give rise to collective dipolar magnetic excitations called magnons. Likewise, multiple spin-flips can give rise to multipolar magnetic excitations in magnetic materials with spin S ≥ 1. Unfortunately, since most experimental probes are governed by dipolar selection rules, collective multipolar excitations have generally remained elusive. For instance, only dipolar magnetic excitations have been observed in isotropic S = 1 Haldane spin systems. Here, we unveil a hidden quadrupolar constituent of the spin dynamics in antiferromagnetic S = 1 Haldane chain material Y2BaNiO5 using Ni L3-edge resonant inelastic x-ray scattering. Our results demonstrate that pure quadrupolar magnetic excitations can be probed without direct interactions with dipolar excitations or anisotropic perturbations. Originating from on-site double spin-flip processes, the quadrupolar magnetic excitations in Y2BaNiO5 show a remarkable dual nature of collective dispersion. While one component propagates as non-interacting entities, the other behaves as a bound quadrupolar magnetic wave. This result highlights the rich and largely unexplored physics of higher-order magnetic excitations.
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Apr 2022
|
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I21-Resonant Inelastic X-ray Scattering (RIXS)
|
Ke-Jin
Zhou
,
Andrew
Walters
,
Mirian
Garcia-Fernandez
,
Thomas
Rice
,
Matthew
Hand
,
Abhishek
Nag
,
Jiemin
Li
,
Stefano
Agrestini
,
Peter
Garland
,
Hongchang
Wang
,
Simon
Alcock
,
Ioana
Nistea
,
Brian
Nutter
,
Nicholas
Rubies
,
Giles
Knap
,
Martin
Gaughran
,
Fajin
Yuan
,
Peter
Chang
,
John
Emmins
,
George
Howell
Open Access
Abstract: The I21 beamline at Diamond Light Source is dedicated to advanced resonant inelastic X-ray scattering (RIXS) for probing charge, orbital, spin and lattice excitations in materials across condensed matter physics, applied sciences and chemistry. Both the beamline and the RIXS spectrometer employ divergent variable-line-spacing gratings covering a broad energy range of 280–3000 eV. A combined energy resolution of ∼35 meV (16 meV) is readily achieved at 930 eV (530 eV) owing to the optimized optics and the mechanics. Considerable efforts have been paid to the design of the entire beamline, particularly the implementation of the collection mirrors, to maximize the X-ray photon throughput. The continuous rotation of the spectrometer over 150° under ultra high vacuum and a cryogenic manipulator with six degrees of freedom allow accurate mappings of low-energy excitations from solid state materials in momentum space. Most importantly, the facility features a unique combination of the high energy resolution and the high photon throughput vital for advanced RIXS applications. Together with its stability and user friendliness, I21 has become one of the most sought after RIXS beamlines in the world.
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Mar 2022
|
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I21-Resonant Inelastic X-ray Scattering (RIXS)
|
M.
Rossi
,
H.
Lu
,
A.
Nag
,
D.
Li
,
M.
Osada
,
K.
Lee
,
B. Y.
Wang
,
S.
Agrestini
,
Mirian
Garcia-Fernandez
,
J. J.
Kas
,
Y.-D.
Chuang
,
Z. X.
Shen
,
H. Y.
Hwang
,
B.
Moritz
,
Ke-Jin
Zhou
,
T. P.
Devereaux
,
W. S.
Lee
Diamond Proposal Number(s):
[25165]
Abstract: The recent discovery of superconductivity in Nd1−xSrxNiO2 has drawn significant attention in the field. A key open question regards the evolution of the electronic structure with respect to hole doping. Here we exploit x-ray absorption spectroscopy (XAS) and resonant inelastic x-ray scattering (RIXS) to probe the doping-dependent electronic structure of Nd1−xSrxNiO. Upon doping, a high-energy feature in Ni L3-edge XAS develops in addition to the main absorption peak, while XAS at the O K-, Nd M3- and Nd M5-edge exhibits a much weaker response. This implies that doped holes are mainly introduced into Ni 3 d states. By comparing our data to atomic multiplet calculations including D4h crystal field, the doping-induced feature in Ni L3-edge XAS is consistent with a d 8 spin-singlet state in which doped holes reside in the 3dx2−y2 orbitals. This is further supported by the softening of RIXS orbital excitations due to doping, corroborating with the Fermi level shift associated with increasing holes in the Ni 3dx2−y2 orbital.
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Dec 2021
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