I21-Resonant Inelastic X-ray Scattering (RIXS)
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Xunyang
Hong
,
Yuetong
Wu
,
Izabela
Bialo
,
Ying
Chan
,
Sze Tung
Li
,
Leonardo
Martinelli
,
Orion
Gerguri
,
Annabella
Drewanowski
,
Qiang
Gao
,
Xiaolin
Ren
,
Xingjiang
Zhou
,
Zhihai
Zhu
,
Alice
Galdi
,
Darrell G.
Schlom
,
Kyle M.
Shen
,
Jaewon
Choi
,
Mirian
Garcia-Fernandez
,
Ke-Jin
Zhou
,
Nicholas B.
Brookes
,
Henrikm.
Ronnow
,
Qisi
Wang
,
Johan
Chang
Diamond Proposal Number(s):
[30189]
Open Access
Abstract: Optimization of unconventional superconductivity involves a balance of interaction strengths. Precise determination of correlation strength across different material families is therefore important. Here, we present a combined X-ray absorption spectroscopy (XAS) and resonant inelastic X-ray scattering (RIXS) study of infinite-layer PrNiO2 and SrCuO2 that enables fair comparison of their interaction strengths. For both compounds, we study the orbital and magnetic excitations and extract their dispersions along high-symmetry directions. Using a single-band Hubbard model and including physically plausible assumptions about higher-order exchange interactions, we estimate the correlation factor U/t for both compounds. A key finding is that despite the prediction of a smaller Coulomb repulsion U, PrNiO2 exhibits a correlation strength U/t that is 20% stronger than that of its isostructural cuprate counterpart SrCuO2. This indicates that moderation of the correlation strength may further optimize superconductivity in nickelates.
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May 2026
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I21-Resonant Inelastic X-ray Scattering (RIXS)
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Yujie
Yan
,
Ying
Chan
,
Xunyang
Hong
,
S. Lin Er
Chow
,
Zhaoyang
Luo
,
Yuehong
Li
,
Tianren
Wang
,
Yuetong
Wu
,
Izabela
Bialo
,
Nurul
Fitriyah
,
Saurav
Prakash
,
Xing
Gao
,
King Yau
Yip
,
Qiang
Gao
,
Xiaolin
Ren
,
Jaewon
Choi
,
Ganesha
Channagowdra
,
Jun
Okamoto
,
Xingjiang
Zhou
,
Zhihai
Zhu
,
Liang
Si
,
Mirian
Garcia-Fernandez
,
Ke-Jin
Zhou
,
Hsiao-Yu
Huang
,
Di-Jing
Huang
,
Johan
Chang
,
Ariando
Ariando
,
Qisi
Wang
Diamond Proposal Number(s):
[30189]
Open Access
Abstract: The recent discovery of high-temperature superconductivity in hole-doped SmNiO2, exhibiting the record-high transition temperature Tc among infinite-layer (IL) nickelates, has opened a new avenue for exploring design principles of superconductivity. Experimentally determining the electronic structure and magnetic interactions in this new system is crucial to elucidating the mechanism behind the enhanced superconductivity. Here, we report a Ni L-edge resonant inelastic x-ray scattering (RIXS) study of superconducting Sm-based IL nickelate thin films Sm1−x−yEuxCayNiO2 (SECNO). Dispersive paramagnonic excitations are observed in both optimally and overdoped SECNO samples, supporting a spin-fluctuation-mediated pairing scenario. However, despite the two-fold enhancement of Tc in the Sm-based nickelates compared to their Pr-based counterparts, the effective exchange coupling strength is reduced by approximately 20%. This behavior contrasts with hole-doped cuprates, where magnetic interactions correlate positively with Tc, highlighting essential differences in their superconducting mechanisms.
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May 2026
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I21-Resonant Inelastic X-ray Scattering (RIXS)
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L.
Martinelli
,
I.
Biało
,
X.
Hong
,
J.
Oppliger
,
C.
Lin
,
T,
Schaller
,
J.
Küspert
,
M. H.
Fischer
,
T.
Kurosawa
,
N.
Momono
,
M.
Oda
,
D. V.
Novikov
,
A.
Khadiev
,
E.
Weschke
,
J.
Choi
,
S.
Agrestini
,
Mirian
Garcia-Fernandez
,
Ke-Jin
Zhou
,
Q.
Wang
,
J.
Chang
Diamond Proposal Number(s):
[33512]
Open Access
Abstract: We use uniaxial strain in combination with ultra-high-resolution resonant inelastic x-ray scattering (RIXS) at the oxygen-𝐾 and copper-𝐿3 edges to study the excitations stemming from the charge ordering wave vector in La1.875Sr0.125CuO4. By detwinning stripe ordering, we demonstrate that the optical phonon anomalies do not show any stripe anisotropy. The low-energy charge excitations also retain an in-plane fourfold symmetry. As such, we find that both phonon and charge excitations are decoupled entirely from the strength of static charge ordering. The almost isotropic character of charge excitations is indicative of a quantum critical behavior and remains a possible source for the strange metal properties found in the normal state of cuprate superconductors.
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Jul 2025
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I21-Resonant Inelastic X-ray Scattering (RIXS)
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Karin
Von Arx
,
Pascal
Rothenbühler
,
Qisi
Wang
,
Leonardo
Martinelli
,
Jaewon
Choi
,
Mirian
Garcia-Fernandez
,
Stefano
Agrestini
,
Ke-Jin
Zhou
,
Antonio
Vecchione
,
Rosalba
Fittipaldi
,
Yasmine
Sassa
,
Mario
Cuoco
,
Filomena
Forte
,
Johan
Chang
Diamond Proposal Number(s):
[27638]
Open Access
Abstract: Multi-band Mott insulators with moderate spin-orbit and Hund’s coupling are key reference points for theoretical concept developments of correlated electron systems. The ruthenate Mott insulator Ca2RuO4 has therefore been intensively studied by spectroscopic probes. However, it has been challenging to resolve the fundamental excitations emerging from the hierarchy of electronic energy scales. Here we apply high resolution resonant inelastic x-ray scattering to probe deeper into the low-energy electronic excitations found in Ca2RuO4. In this fashion, we probe a series of spin-orbital excitations. By taking advantage of enhanced energy resolution, we probe a 40 meV mode through the oxygen K-edge. The polarization dependence of this low-energy excitations exposes a distinct orbital nature, originating from the interplay of spin-orbit coupling and octahedral rotations. Additionally, we discuss the role of magnetic correlations to describe the occurrence of excitations with amplitudes which are multiple of a given energy. Such direct determination of relevant electronic energy scales sharpens the target for theory developments of Mott insulators’ orbital degree of freedom.
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May 2025
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I05-ARPES
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Ola Kenji
Forslund
,
Xiaoxiong
Liu
,
Soohyeon
Shin
,
Chun
Lin
,
Masafumi
Horio
,
Qisi
Wang
,
Kevin
Kramer
,
Saumya
Mukherjee
,
Timur
Kim
,
Cephise
Cacho
,
Chennan
Wang
,
Tian
Shang
,
Victor
Ukleev
,
Jonathan S.
White
,
Pascal
Puphal
,
Yasmine
Sassa
,
Ekaterina
Pomjakushina
,
Titus
Neupert
,
Johan
Chang
Diamond Proposal Number(s):
[22091]
Open Access
Abstract: The anomalous Hall effect (AHE) has emerged as a key indicator of time-reversal symmetry breaking (TRSB) and topological features in electronic band structures. Absent of a magnetic field, the AHE requires spontaneous TRSB but has proven hard to probe due to averaging over domains. The anomalous component of the Hall effect is thus frequently derived from extrapolating the magnetic field dependence of the Hall response. We show that discerning whether the AHE is an intrinsic property of the field-free system becomes intricate in the presence of strong magnetic fluctuations. As a study case, we use the Weyl semimetal PrAlGe, where TRSB can be toggled via a ferromagnetic transition, providing a transparent view of the AHE’s topological origin. Through a combination of thermodynamic, transport, and muon spin relaxation measurements, we contrast the behavior below the ferromagnetic transition temperature to that of strong magnetic fluctuations above. Our results on PrAlGe provide general insights into the interpretation of anomalous Hall signals in systems where TRSB is debated, such as families of kagome metals or certain transition metal dichalcogenides.
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Mar 2025
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I05-ARPES
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Chun
Lin
,
Armando
Consiglio
,
Ola Kenji
Forslund
,
Julia
Kuespert
,
M. Michael
Denner
,
Hechang
Lei
,
Alex
Louat
,
Matthew D.
Watson
,
Timur K.
Kim
,
Cephise
Cacho
,
Dina
Carbone
,
Mats
Leandersson
,
Craig
Polley
,
Thiagarajan
Balasubramanian
,
Domenico
Di Sante
,
Ronny
Thomale
,
Zurab
Guguchia
,
Giorgio
Sangiovanni
,
Titus
Neupert
,
Johan
Chang
Diamond Proposal Number(s):
[30650, 33528]
Open Access
Abstract: Tunable quantum materials hold great potential for applications. Of special interest are materials in which small lattice strain induces giant electronic responses. The kagome compounds AV3Sb5 (A = K, Rb, Cs) provide a testbed for electronic tunable states. In this study, through angle-resolved photoemission spectroscopy, we provide comprehensive spectroscopic measurements of the electronic responses induced by compressive and tensile strains on the charge-density-wave (CDW) and van Hove singularity (VHS) in CsV3Sb5. We observe a tripling of the CDW gap magnitudes with ~ 1% strain. Simultaneously, changes of both energy and mass of the VHS are observed. Combined, this reveals an anticorrelation between the unconventional CDW order parameter and the mass of the VHS, and highlight the role of the latter in the superconducting pairing. The substantial electronic responses uncover a rich strain tunability of the versatile kagome system in studying quantum interplays under lattice variations.
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Dec 2024
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I21-Resonant Inelastic X-ray Scattering (RIXS)
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Izabela
Bialo
,
Leonardo
Martinelli
,
Gabriele
De Luca
,
Paul
Worm
,
Annabella
Drewanowski
,
Simon
Jöhr
,
Jaewon
Choi
,
Mirian
Garcia-Fernandez
,
Stefano
Agrestini
,
Ke-Jin
Zhou
,
Kurt
Kummer
,
Nicholas B.
Brookes
,
Luo
Guo
,
Anthony
Edgeton
,
Chang B.
Eom
,
Jan M.
Tomczak
,
Karsten
Held
,
Marta
Gibert
,
Qisi
Wang
,
Johan
Chang
Diamond Proposal Number(s):
[30189]
Open Access
Abstract: Magnetic frustration is a route for novel ground states, including spin liquids and spin ices. Such frustration can be introduced through either lattice geometry or incompatible exchange interactions. Here, we find that epitaxial strain is an effective tool for tuning antiferromagnetic exchange interactions in a square-lattice system. By studying the magnon excitations in La2NiO4 films using resonant inelastic x-ray scattering, we show that the magnon displays substantial dispersion along the antiferromagnetic zone boundary, at energies that depend on the lattice of the film’s substrate. Using first principles simulations and an effective spin model, we demonstrate that the antiferromagnetic next-nearest neighbour coupling is a consequence of the two-orbital nature of La2NiO4. Altogether, we illustrate that compressive epitaxial strain enhances this coupling and, as a result, increases the level of incompatibility between exchange interactions within a model square-lattice system.
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Jul 2024
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I21-Resonant Inelastic X-ray Scattering (RIXS)
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Qiang
Gao
,
Shiyu
Fan
,
Qisi
Wang
,
Jiarui
Li
,
Xiaolin
Ren
,
Izabela
Bialo
,
Annabella
Drewanowski
,
Pascal
Rothenbühler
,
Jaewon
Choi
,
Ronny
Sutarto
,
Yao
Wang
,
Tao
Xiang
,
Jiangping
Hu
,
Ke-Jin
Zhou
,
Valentina
Bisogni
,
Riccardo
Comin
,
Johan
Chang
,
Jonathan
Pelliciari
,
Xingjiang
Zhou
,
Zhihai
Zhu
Diamond Proposal Number(s):
[30189]
Open Access
Abstract: Strongly correlated materials respond sensitively to external perturbations such as strain, pressure, and doping. In the recently discovered superconducting infinite-layer nickelates, the superconducting transition temperature can be enhanced via only ~ 1% compressive strain-tuning with the root of such enhancement still being elusive. Using resonant inelastic x-ray scattering (RIXS), we investigate the magnetic excitations in infinite-layer PrNiO2 thin films grown on two different substrates, namely SrTiO3 (STO) and (LaAlO3)0.3(Sr2TaAlO6)0.7 (LSAT) enforcing different strain on the nickelates films. The magnon bandwidth of PrNiO2 shows only marginal response to strain-tuning, in sharp contrast to the enhancement of the superconducting transition temperature Tc in the doped superconducting samples. These results suggest the bandwidth of spin excitations of the parent compounds is similar under strain while Tc in the doped ones is not, and thus provide important empirics for the understanding of superconductivity in infinite-layer nickelates.
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Jul 2024
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I21-Resonant Inelastic X-ray Scattering (RIXS)
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Paul
Worm
,
Qisi
Wang
,
Motoharu
Kitatani
,
Izabela
Bialo
,
Qiang
Gao
,
Xiaolin
Ren
,
Jaewon
Choi
,
Diana
Csontosová
,
Ke-Jin
Zhou
,
Xingjiang
Zhou
,
Zhihai
Zhu
,
Liang
Si
,
Johan
Chang
,
Jan M.
Tomczak
,
Karsten
Held
Diamond Proposal Number(s):
[30189]
Abstract: Infinite-layer nickelates show high-temperature superconductivity, and the experimental phase diagram agrees well with the one simulated within the dynamical vertex approximation (DΓA). Here, we compare the spin-fluctuation spectrum behind these calculations to resonant inelastic x-ray scattering experiments. The overall agreement is good. This independent cross validation of the strength of spin fluctuations strongly supports the scenario, advanced by DΓA, that spin fluctuations are the mediator of the superconductivity observed in nickelates.
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Jun 2024
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I05-ARPES
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Carolina A.
Marques
,
Philip A. E.
Murgatroyd
,
Rosalba
Fittipaldi
,
Weronika
Osmolska
,
Brendan
Edwards
,
Izidor
Benedičič
,
Gesa-R.
Siemann
,
Luke C.
Rhodes
,
Sebastian
Buchberger
,
Masahiro
Naritsuka
,
Edgar
Abarca-Morales
,
Daniel
Halliday
,
Craig
Polley
,
Mats
Leandersson
,
Masafumi
Horio
,
Johan
Chang
,
Raja
Arumugam
,
Mariateresa
Lettieri
,
Veronica
Granata
,
Antonio
Vecchione
,
Phil D. C.
King
,
Peter
Wahl
Diamond Proposal Number(s):
[28412]
Open Access
Abstract: Van Hove singularities (VHss) in the vicinity of the Fermi energy often play a dramatic role in the physics of strongly correlated electron materials. The divergence of the density of states generated by VHss can trigger the emergence of phases such as superconductivity, ferromagnetism, metamagnetism, and density wave orders. A detailed understanding of the electronic structure of these VHss is therefore essential for an accurate description of such instabilities. Here, we study the low-energy electronic structure of the trilayer strontium ruthenate Sr4Ru3O10, identifying a rich hierarchy of VHss using angle-resolved photoemission spectroscopy and millikelvin scanning tunneling microscopy. Comparison of k-resolved electron spectroscopy and quasiparticle interference allows us to determine the structure of the VHss and demonstrate the crucial role of spin-orbit coupling in shaping them. We use this to develop a minimal model from which we identify a mechanism for driving a field-induced Lifshitz transition in ferromagnetic metals.
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Apr 2024
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