I05-ARPES
|
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.
|
Apr 2024
|
|
I05-ARPES
|
Masafumi
Horio
,
Filomena
Forte
,
Denys
Sutter
,
Minjae
Kim
,
Claudia G.
Fatuzzo
,
Christian E.
Matt
,
Simon
Moser
,
Tetsuya
Wada
,
Veronica
Granata
,
Rosalba
Fittipaldi
,
Yasmine
Sassa
,
Gianmarco
Gatti
,
Henrik M.
Ronnow
,
Moritz
Hoesch
,
Timur K.
Kim
,
Chris
Jozwiak
,
Aaron
Bostwick
,
Eli
Rotenberg
,
Iwao
Matsuda
,
Antoine
Georges
,
Giorgio
Sangiovanni
,
Antonio
Vecchione
,
Mario
Cuoco
,
Johan
Chang
Diamond Proposal Number(s):
[10550]
Open Access
Abstract: Doped Mott insulators are the starting point for interesting physics such as high temperature superconductivity and quantum spin liquids. For multi-band Mott insulators, orbital selective ground states have been envisioned. However, orbital selective metals and Mott insulators have been difficult to realize experimentally. Here we demonstrate by photoemission spectroscopy how Ca2RuO4, upon alkali-metal surface doping, develops a single-band metal skin. Our dynamical mean field theory calculations reveal that homogeneous electron doping of Ca2RuO4 results in a multi-band metal. All together, our results provide evidence for an orbital-selective Mott insulator breakdown, which is unachievable via simple electron doping. Supported by a cluster model and cluster perturbation theory calculations, we demonstrate a type of skin metal-insulator transition induced by surface dopants that orbital-selectively hybridize with the bulk Mott state and in turn produce coherent in-gap states.
|
Nov 2023
|
|
I05-ARPES
|
Kevin P.
Kramer
,
Rina
Tazai
,
Karin
Von Arx
,
Masafumi
Horio
,
Julia
Küspert
,
Qisi
Wang
,
Yasmine
Sassa
,
Timur K.
Kim
,
Cephise
Cacho
,
Julien E.
Rault
,
Patrick
Le Fèvre
,
François
Bertran
,
Marc
Janoschek
,
Nicolas
Gauthier
,
Daniel
Mazzone
,
Ramzy
Daou
,
Johan
Chang
Open Access
Abstract: We present a resonant angle-resolved photoemission spectroscopy (ARPES) study of the electronic band structure and heavy fermion quasiparticles in CeRu2Si2. Using light polarization analysis, considerations of the crystal field environment and hybridization between conduction and f electronic states, we identify the d-electronic orbital character of conduction bands crossing the Fermi level. Resonant ARPES spectra suggest that the localized Ce f states hybridize with eg and t2g states around the zone center. In this fashion, we reveal the orbital structure of the heavy fermion quasiparticles in CeRu2Si2 and discuss its implications for metamagnetism and superconductivity in the related compound CeCu2Si2.
|
Oct 2023
|
|
I05-ARPES
|
J.
Küspert
,
R.
Cohn Wagner
,
C.
Lin
,
K.
Von Arx
,
Q.
Wang
,
K.
Kramer
,
W. R.
Pudelko
,
N. C.
Plumb
,
C. E.
Matt
,
C. G.
Fatuzzo
,
D.
Sutter
,
Y.
Sassa
,
J.-Q.
Yan
,
J.-S.
Zhou
,
J. B.
Goodenough
,
S.
Pyon
,
T.
Takayama
,
H.
Takagi
,
T.
Kurosawa
,
N.
Momono
,
M.
Oda
,
M.
Hoesch
,
C.
Cacho
,
T. K.
Kim
,
M.
Horio
,
J.
Chang
Diamond Proposal Number(s):
[27768, 10550]
Open Access
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
La
2
−
x
Sr
x
CuO
4
,
La
1.6
−
x
Nd
0.4
Sr
x
CuO
4
, and
La
1.8
−
x
Eu
0.2
Sr
x
CuO
4
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.
|
Oct 2022
|
|
I05-ARPES
|
C. E.
Matt
,
O.
Ivashko
,
M.
Horio
,
J.
Choi
,
Q.
Wang
,
D.
Sutter
,
N.
Dennler
,
M. H.
Fischer
,
S.
Katrych
,
L.
Forro
,
J.
Ma
,
B.
Fu
,
B. Q.
Lv
,
M. V.
Zimmermann
,
T. K.
Kim
,
N. C.
Plumb
,
N.
Xu
,
M.
Shi
,
Johan
Chang
Diamond Proposal Number(s):
[16104]
Open Access
Abstract: The interplay between structural and electronic phases in iron-based superconductors is a central theme in the search for the superconducting pairing mechanism. While electronic nematicity is competing with superconductivity, the effect of purely structural orthorhombic order is unexplored. Here, using x-ray diffraction and angle-resolved photoemission spectroscopy, we reveal a structural orthorhombic phase in the electron-doped iron-pnictide superconductor
Pr
4
Fe
2
As
2
Te
0.88
O
4
(
T
c
=
25
K), which is distinct from orthorhombicity in the nematic phase in underdoped pnictides. Despite the high electron doping we find an exceptionally high orthorhombic onset temperature (
T
ort
∼
250
K), no signatures of phase competition with superconductivity, and absence of electronic nematic order as the driving mechanism for orthorhombicity. Combined, our results establish a high-temperature phase in the phase diagram of iron-pnictide superconductors and impose strong constraints for the modeling of their superconducting pairing mechanism.
|
Jun 2021
|
|
I21-Resonant Inelastic X-ray Scattering (RIXS)
|
Qisi
Wang
,
Karin
Von Arx
,
Masafumi
Horio
,
Deepak John
Mukkattukavil
,
Julia
Kuespert
,
Yasmine
Sassa
,
Thorsten
Schmitt
,
Abhishek
Nag
,
Sunseng
Pyon
,
Tomohiro
Takayama
,
Hidenori
Takagi
,
Mirian
Garcia-Fernandez
,
Ke-Jin
Zhou
,
Johan
Chang
Diamond Proposal Number(s):
[24481]
Open Access
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 bond-stretching phonon mode in stripe-ordered cuprate La1.675Eu0.2Sr0.125CuO4. 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.
|
Jun 2021
|
|
I05-ARPES
|
M.
Horio
,
Q.
Wang
,
V.
Granata
,
K. P.
Kramer
,
Y.
Sassa
,
S.
Jöhr
,
D.
Sutter
,
A.
Bold
,
L.
Das
,
Y.
Xu
,
R.
Frison
,
R.
Fittipaldi
,
T. K.
Kim
,
C.
Cacho
,
J. E.
Rault
,
P. Le
Fèvre
,
F.
Bertran
,
N. C.
Plumb
,
M.
Shi
,
A.
Vecchione
,
M. H.
Fischer
,
J.
Chang
Diamond Proposal Number(s):
[20259]
Open Access
Abstract: Electronic band structures in solids stem from a periodic potential reflecting the structure of either the crystal lattice or electronic order. In the stoichiometric ruthenate Ca3Ru2O7, numerous Fermi surface-sensitive probes indicate a low-temperature electronic reconstruction. Yet, the causality and the reconstructed band structure remain unsolved. Here, we show by angle-resolved photoemission spectroscopy, how in Ca3Ru2O7 a C2-symmetric massive Dirac semimetal is realized through a Brillouin-zone preserving electronic reconstruction. This Dirac semimetal emerges in a two-stage transition upon cooling. The Dirac point and band velocities are consistent with constraints set by quantum oscillation, thermodynamic, and transport experiments, suggesting that the complete Fermi surface is resolved. The reconstructed structure—incompatible with translational-symmetry-breaking density waves—serves as an important test for band structure calculations of correlated electron systems.
|
Mar 2021
|
|
I21-Resonant Inelastic X-ray Scattering (RIXS)
|
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.
|
May 2020
|
|
I05-ARPES
|
D.
Sutter
,
M.
Kim
,
C. E.
Matt
,
M.
Horio
,
R.
Fittipaldi
,
A.
Vecchione
,
V.
Granata
,
K.
Hauser
,
Y.
Sassa
,
G.
Gatti
,
M.
Grioni
,
M.
Hoesch
,
T. K.
Kim
,
E.
Rienks
,
N. C.
Plumb
,
M.
Shi
,
T.
Neupert
,
A.
Georges
,
J.
Chang
Diamond Proposal Number(s):
[15296]
Abstract: We present a comprehensive angle-resolved photoemission spectroscopy study of
Ca
1.8
Sr
0.2
RuO
4
. Four distinct bands are revealed and along the Ru-O bond direction their orbital characters are identified through a light polarization analysis and comparison to dynamical mean-field theory calculations. Bands assigned to
d
x
z
,
d
y
z
orbitals display Fermi liquid behavior with fourfold quasiparticle mass renormalization. Extremely heavy fermions—associated with a predominantly
d
x
y
band character—are shown to display non-Fermi-liquid behavior. We thus demonstrate that
Ca
1.8
Sr
0.2
RuO
4
is a hybrid metal with an orbitally selective Fermi liquid quasiparticle breakdown.
|
Mar 2019
|
|
I05-ARPES
|
C. E.
Matt
,
D.
Sutter
,
A. M.
Cook
,
Y.
Sassa
,
Martin
Mansson
,
O.
Tjernberg
,
L.
Das
,
M.
Horio
,
D.
Destraz
,
C. G.
Fatuzzo
,
K.
Hauser
,
M.
Shi
,
M.
Kobayashi
,
V. N.
Strocov
,
T.
Schmitt
,
P.
Dudin
,
M.
Hoesch
,
S.
Pyon
,
T.
Takayama
,
H.
Takagi
,
O. J.
Lipscombe
,
S. M.
Hayden
,
T.
Kurosawa
,
N.
Momono
,
M.
Oda
,
T.
Neupert
,
J.
Chang
Diamond Proposal Number(s):
[10550]
Open Access
Abstract: The minimal ingredients to explain the essential physics of layered copper-oxide (cuprates) materials remains heavily debated. Effective low-energy single-band models of the copper–oxygen orbitals are widely used because there exists no strong experimental evidence supporting multi-band structures. Here, we report angle-resolved photoelectron spectroscopy experiments on La-based cuprates that provide direct observation of a two-band structure. This electronic structure, qualitatively consistent with density functional theory, is parametrised by a two-orbital (d x 2 −y 2
dx2-y2
and d z 2
dz2
) tight-binding model. We quantify the orbital hybridisation which provides an explanation for the Fermi surface topology and the proximity of the van-Hove singularity to the Fermi level. Our analysis leads to a unification of electronic hopping parameters for single-layer cuprates and we conclude that hybridisation, restraining d-wave pairing, is an important optimisation element for superconductivity.
|
Mar 2018
|
|
