Detectors
|
J.
Correa
,
M.
Mehrjoo
,
R.
Battistelli
,
F.
Lehmkühler
,
A.
Marras
,
C. B.
Wunderer
,
T.
Hirono
,
V.
Felk
,
F.
Krivan
,
S.
Lange
,
I.
Shevyakov
,
V.
Vardanyan
,
M.
Zimmer
,
M.
Hoesch
,
K.
Bagschik
,
N.
Guerrini
,
B.
Marsh
,
I.
Sedgwick
,
G.
Cautero
,
L.
Stebel
,
D.
Giuressi
,
R. H.
Menk
,
A.
Greer
,
T.
Nicholls
,
W.
Nichols
,
U.
Pedersen
,
P.
Shikhaliev
,
N.
Tartoni
,
H. J.
Hyun
,
S. H.
Kim
,
S. Y.
Park
,
K. S.
Kim
,
F.
Orsini
,
F. J.
Iguaz
,
F.
Büttner
,
B.
Pfau
,
E.
Plönjes
,
K.
Kharitonov
,
M.
Ruiz-Lopez
,
R.
Pan
,
S.
Gang
,
B.
Keitel
,
H.
Graafsma
Open Access
Abstract: The PERCIVAL detector is a CMOS imager designed for the soft X-ray regime at photon sources. Although still in its final development phase, it has recently seen its first user experiments: ptychography at a free-electron laser, holographic imaging at a storage ring and preliminary tests on X-ray photon correlation spectroscopy. The detector performed remarkably well in terms of spatial resolution achievable in the sample plane, owing to its small pixel size, large active area and very large dynamic range; but also in terms of its frame rate, which is significantly faster than traditional CCDs. In particular, it is the combination of these features which makes PERCIVAL an attractive option for soft X-ray science.
|
Jan 2023
|
|
I09-Surface and Interface Structural Analysis
|
Adam J.
Jackson
,
Benjamin J.
Parrett
,
Joe
Willis
,
Alex M.
Ganose
,
W. W. Winnie
Leung
,
Yuhan
Liu
,
Benjamin A. D.
Williamson
,
Timur K.
Kim
,
Moritz
Hoesch
,
Larissa S. I.
Veiga
,
Raman
Kalra
,
Jens
Neu
,
Charles A.
Schmuttenmaer
,
Tien-Lin
Lee
,
Anna
Regoutz
,
Tung-Chun
Lee
,
Tim D.
Veal
,
Robert G.
Palgrave
,
Robin
Perry
,
David O.
Scanlon
Diamond Proposal Number(s):
[24449]
Open Access
Abstract: Transparent conducting oxides have become ubiquitous in modern optoelectronics. However, the number of oxides that are transparent to visible light and have the metallic-like conductivity necessary for applications is limited to a handful of systems that have been known for the past 40 years. In this work, we use hybrid density functional theory and defect chemistry analysis to demonstrate that tri-rutile zinc antimonate, ZnSb2O6, is an ideal transparent conducting oxide and to identify gallium as the optimal dopant to yield high conductivity and transparency. To validate our computational predictions, we have synthesized both powder samples and single crystals of Ga-doped ZnSb2O6 which conclusively show behavior consistent with a degenerate transparent conducting oxide. This study demonstrates the possibility of a family of Sb(V)-containing oxides for transparent conducting oxide and power electronics applications.
|
Oct 2022
|
|
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
|
F.
Mazzola
,
C.-M.
Yim
,
V.
Sunko
,
S.
Khim
,
P.
Kushwaha
,
O. J.
Clark
,
L.
Bawden
,
I.
Markovic
,
D.
Chakraborti
,
T. K.
Kim
,
M.
Hoesch
,
A. P.
Mackenzie
,
P.
Wahl
,
P. D. C.
King
Diamond Proposal Number(s):
[12469, 14927, 1626]
Open Access
Abstract: Controlling spin wave excitations in magnetic materials underpins the burgeoning field of magnonics. Yet, little is known about how magnons interact with the conduction electrons of itinerant magnets, or how this interplay can be controlled. Via a surface-sensitive spectroscopic approach, we demonstrate a strong electron–magnon coupling at the Pd-terminated surface of the delafossite oxide PdCoO2, where a polar surface charge mediates a Stoner transition to itinerant surface ferromagnetism. We show how the coupling is enhanced sevenfold with increasing surface disorder, and concomitant charge carrier doping, becoming sufficiently strong to drive the system into a polaronic regime, accompanied by a significant quasiparticle mass enhancement. Our study thus sheds light on electron–magnon interactions in solid-state materials, and the ways in which these can be controlled.
|
Feb 2022
|
|
I05-ARPES
|
Y.
Falke
,
N.
Ehlen
,
G.
Marini
,
A. V.
Fedorov
,
V. Y.
Voroshnin
,
B. V.
Senkovskiy
,
K.
Nikonov
,
M.
Hoesch
,
T. K.
Kim
,
L.
Petaccia
,
G.
Di Santo
,
T.
Szkopek
,
G.
Profeta
,
A.
Gruneis
Diamond Proposal Number(s):
[17064]
Abstract: We investigate electron-phonon coupling (EPC) in the charge density wave (CDW) phase of
V
Se
2
by Raman spectroscopy, angle-resolved photoemission spectroscopy (ARPES), and ab initio calculations. Zone folding induced by the
4
×
4
in-plane CDW phase promotes the appearance of a Raman peak at
∼
170
cm
−
1
. The suppression of ARPES intensity in parts of the Fermi surface is also a result of CDW-induced zone folding and anticrossing of the electron energy bands. The appearance of the new Raman peak is in line with the ARPES observation of a kink feature in the spectral function at the same energy. A self-energy analysis yields an EPC constant of
λ
=
0.3
. Our calculations of the EPC are in excellent agreement and reveal that the kink is caused by several optical phonon branches close in energy. Our paper highlights the CDW phase as a means of inducing EPC pathways to optical phonons that directly affect its Raman spectrum.
|
Dec 2021
|
|
Detectors
|
Alessandro
Marras
,
Jonathan
Correa
,
Sabine
Lange
,
Vahagn
Vardanyan
,
Tim
Gerhardt
,
Manuela
Kuhn
,
Frantisek
Krivan
,
Igor
Shevyakov
,
Manfred
Zimmer
,
Moritz
Hoesch
,
Kai
Bagschik
,
Frank
Scholz
,
Niccolo
Guerrini
,
Ben
Marsh
,
Iain
Sedgwick
,
Giuseppe
Cautero
,
Dario
Giuressi
,
Gregori
Iztok
,
Ralf H.
Menk
,
Martin
Scarcia
,
Luigi
Stebel
,
Tim
Nicholls
,
William
Nichols
,
Ulrik K.
Pedersen
,
Polad
Shikhaliev
,
Nicola
Tartoni
,
Hyojung
Hyun
,
Seonghan
Kim
,
Kyungsook
Kim
,
Seungyu
Rah
,
Arkadiusz
Dawiec
,
Fabienne
Orsini
,
Giovanni
Pinaroli
,
Alan
Greer
,
Steve
Aplin
,
April D.
Jewell
,
Todd J.
Jones
,
Shouleh
Nikzad
,
Michael E.
Hoenk
,
Frank
Okrent
,
Heinz
Graafsma
,
Cornelia B.
Wunderer
Open Access
Abstract: In this paper the back-side-illuminated Percival 2-Megapixel (P2M) detector is presented, along with its characterization by means of optical and X-ray photons. For the first time, the response of the system to soft X-rays (250 eV to 1 keV) is presented. The main performance parameters of the first detector are measured, assessing the capabilities in terms of noise, dynamic range and single-photon discrimination capability. Present limitations and coming improvements are discussed.
|
Jan 2021
|
|
I05-ARPES
|
I.
Cucchi
,
A.
Marrazzo
,
E.
Cappelli
,
S.
Ricco
,
F. Y.
Bruno
,
S.
Lisi
,
M.
Hoesch
,
T. K.
Kim
,
C.
Cacho
,
C.
Besnard
,
E.
Giannini
,
N.
Marzari
,
M.
Gibertini
,
F.
Baumberger
,
A.
Tamai
Diamond Proposal Number(s):
[18952]
Abstract: We report high-resolution angle-resolved photoemission measurements on single crystals of
Pt
2
HgSe
3
grown by high-pressure synthesis. Our data reveal a gapped Dirac nodal line whose (001) projection separates the surface Brillouin zone in topological and trivial areas. In the nontrivial
k
-space range, we find surface states with multiple saddle points in the dispersion, resulting in two van Hove singularities in the surface density of states. Based on density-functional theory calculations, we identify these surface states as signatures of a topological crystalline state, which coexists with a weak topological phase.
|
Feb 2020
|
|
I05-ARPES
|
V. A.
Rogalev
,
F.
Reis
,
F.
Adler
,
M.
Bauernfeind
,
J.
Erhardt
,
A.
Kowalewski
,
M. R.
Scholz
,
L.
Dudy
,
L. B.
Duffy
,
T.
Hesjedal
,
M.
Hoesch
,
G.
Bihlmayer
,
J.
Schäfer
,
R.
Claessen
Diamond Proposal Number(s):
[10244, 10289, 12892, 15285]
Abstract: We report on the electronic structure of
α
-Sn films in the very low thickness regime grown on InSb(111)A. High-resolution low photon energy angle-resolved photoemission spectroscopy allows for the direct observation of the linearly dispersing two-dimensional (2D) topological surface state (TSS) that exists between the second valence band and the conduction band. The Dirac point of this TSS was found to be 200 meV below the Fermi level in 10-nm-thick films, which enables the observation of the hybridization gap opening at the Dirac point of the TSS for thinner films. The crossover to a quasi-2D electronic structure is accompanied by a full gap opening at the Brillouin-zone center, in agreement with our density functional theory calculations. We further identify the thickness regime of
α
-Sn films where the hybridization gap in the TSS coexists with the topologically nontrivial electronic structure and one can expect the presence of a one-dimensional helical edge state.
|
Dec 2019
|
|
I05-ARPES
|
R. C.
Vidal
,
H.
Bentmann
,
T. R. F.
Peixoto
,
A.
Zeugner
,
S.
Moser
,
C.-H.
Min
,
S.
Schatz
,
K.
Kissner
,
M.
Unzelmann
,
C. I.
Fornari
,
H. B.
Vasili
,
M.
Valvidares
,
K.
Sakamoto
,
D.
Mondal
,
J.
Fujii
,
I.
Vobornik
,
S.
Jung
,
C.
Cacho
,
T. K.
Kim
,
R. J.
Koch
,
C.
Jozwiak
,
A.
Bostwick
,
J. D.
Denlinger
,
E.
Rotenberg
,
J.
Buck
,
M.
Hoesch
,
F.
Diekmann
,
S.
Rohlf
,
M.
Kalläne
,
K.
Rossnagel
,
M. M.
Otrokov
,
E. V.
Chulkov
,
M.
Ruck
,
A.
Isaeva
,
F.
Reinert
Diamond Proposal Number(s):
[19278, 22468]
Abstract: The layered van der Waals antiferromagnet
MnBi
2
Te
4
has been predicted to combine the band ordering of archetypical topological insulators such as
Bi
2
Te
3
with the magnetism of Mn, making this material a viable candidate for the realization of various magnetic topological states. We have systematically investigated the surface electronic structure of
MnBi
2
Te
4
(0001) single crystals by use of spin- and angle-resolved photoelectron spectroscopy experiments. In line with theoretical predictions, the results reveal a surface state in the bulk band gap and they provide evidence for the influence of exchange interaction and spin-orbit coupling on the surface electronic structure.
|
Sep 2019
|
|
I05-ARPES
|
Sergey
Borisenko
,
Daniil
Evtushinsky
,
Quinn
Gibson
,
Alexander
Yaresko
,
Klaus
Koepernik
,
Timur
Kim
,
Mazhar
Ali
,
Jeroen
Van Den Brink
,
Moritz
Hoesch
,
Alexander
Fedorov
,
Erik
Haubold
,
Yevhen
Kushnirenko
,
Ivan
Soldatov
,
Rudolf
Schäfer
,
Robert J.
Cava
Diamond Proposal Number(s):
[11643]
Open Access
Abstract: Spectroscopic detection of Dirac and Weyl fermions in real materials is vital for both, promising applications and fundamental bridge between high-energy and condensed-matter physics. While the presence of Dirac and noncentrosymmetric Weyl fermions is well established in many materials, the magnetic Weyl semimetals still escape direct experimental detection. In order to find a time-reversal symmetry breaking Weyl state we design two materials and present here experimental and theoretical evidence of realization of such a state in one of them, YbMnBi2. We model the time-reversal symmetry breaking observed by magnetization and magneto-optical microscopy measurements by canted antiferromagnetism and find a number of Weyl points. Using angle-resolved photoemission, we directly observe two pairs of Weyl points connected by the Fermi arcs. Our results not only provide a fundamental link between the two areas of physics, but also demonstrate the practical way to design novel materials with exotic properties.
|
Jul 2019
|
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