I05-ARPES
|
M.
Berben
,
S.
Smit
,
C.
Duffy
,
Y.-T.
Hsu
,
L.
Bawden
,
F.
Heringa
,
F.
Gerritsen
,
S.
Cassanelli
,
X.
Feng
,
S.
Bron
,
E.
Van Heumen
,
Y.
Huang
,
F.
Bertran
,
T. K.
Kim
,
C.
Cacho
,
A.
Carrington
,
M. S.
Golden
,
N. E.
Hussey
Abstract: Once doped away from their parent Mott insulating state, the hole-doped cuprates enter into many varied and exotic phases. The onset temperature of each phase is then plotted versus
p
—the number of doped holes per copper atom—to form a representative phase diagram. Apart from differences in the absolute temperature scales among the various families, the resultant phase diagrams are strikingly similar. In particular, the
p
values corresponding to optimal doping (
p
opt
∼
0.16
) and to the end of the pseudogap phase
(
p
∗
∼
0.19
–
0.20
)
are essentially the same for all cuprate families bar one: the single-layer Bi-based cuprate
Bi
2
+
z
−
y
Pb
y
Sr
2
−
x
−
z
La
x
CuO
6
+
δ
(Bi2201). This anomaly arises partly due to the complex stoichiometry of this material and also to the different
p
values inferred from disparate (e.g., bulk or surface) measurements performed on samples with comparable superconducting transition temperatures
T
c
. Here, by combining measurements of the in-plane resistivity in zero and high magnetic fields with angle-resolved photoemission spectroscopy studies in the superconducting and normal state, we argue that the phase diagram of Bi2201 may in fact be similar to that realized in other families. This study therefore brings Bi2201 into the fold and supports the notion of universality of
p
opt
and
p
∗
in all hole-doped cuprates.
|
Apr 2022
|
|
I05-ARPES
|
Diamond Proposal Number(s):
[22375]
Abstract: Type-II topological Dirac semimetals are topological quantum materials hosting Lorentz-symmetry breaking type-II Dirac fermions, which are tilted Dirac cones with various exotic physical properties, such as anisotropic chiral anomalies and novel quantum oscillations. Until now, only limited material systems have been confirmed by theory and experiments with the type-II Dirac fermions. Here, we investigated the electronic structure of a new type-II Dirac semimetal VAl3 with angle-resolved photoelectron spectroscopy. The measured band dispersions are consistent with the theoretical prediction, which suggests the Dirac points are located close to (at about 100 meV above) the Fermi level. Our work demonstrates a new type-II Dirac semimetal candidate system with different Dirac node configurations and application potentials.
|
Mar 2022
|
|
I05-ARPES
|
Xian P.
Yang
,
Harrison
Labollita
,
Zi-Jia
Cheng
,
Hari
Bhandari
,
Tyler A.
Cochran
,
Jia-Xin
Yin
,
Md. Shafayat
Hossain
,
Ilya
Belopolski
,
Qi
Zhang
,
Yuxiao
Jiang
,
Nana
Shumiya
,
Daniel
Multer
,
Maksim
Liskevich
,
Dmitry A.
Usanov
,
Yanliu
Dang
,
Vladimir N.
Strocov
,
Albert V.
Davydov
,
Nirmal J.
Ghimire
,
Antia S.
Botana
,
M. Zahid
Hasan
Diamond Proposal Number(s):
[29230]
Abstract: Layered transition metal dichalcogenides have a rich phase diagram and they feature two-dimensionality in numerous physical properties.
Co
1
/
3
NbS
2
is one of the newest members of this family where Co atoms are intercalated into the van der Waals gaps between
NbS
2
layers. We study the three-dimensional electronic band structure of
Co
1
/
3
NbS
2
using both surface and bulk sensitive angle-resolved photoemission spectroscopy. We show that the electronic bands do not fit into the rigid band shift picture after the Co intercalation. Instead,
Co
1
/
3
NbS
2
displays a different orbital character near the Fermi level compared to the pristine
NbS
2
compound and has a clear band dispersion in the
k
z
direction despite its layered structure. Our photoemission study demonstrates the out-of-plane electronic correlations introduced by the Co intercalation, thus offering a different perspective on this compound. Finally, we propose how Fermi level tuning could lead to exotic phases such as spin density wave instability.
|
Mar 2022
|
|
I05-ARPES
|
K.
Huang
,
Z. X.
Li
,
D. P.
Guo
,
H. F.
Yang
,
Y. W.
Li
,
A. J.
Liang
,
F.
Wu
,
L. X.
Xu
,
L. X.
Yang
,
W.
Ji
,
Y. F.
Guo
,
Y. L.
Chen
,
Z. K.
Liu
Abstract: As a van der Waals ferromagnet with high Curie temperature, Fe5-xGeTe2 has attracted tremendous interests recently. Here, using high-resolution angle-resolved photoemission spectroscopy (ARPES), we systematically investigated the electronic structure of Fe5-xGeTe2 crystals and its temperature evolution. Our ARPES measurement reveals two types of bandstructures from two different terminations with slight kz evolution. Interestingly, across the ferromagnetic transition, we observed the merging of two split bands above the Curie temperature, suggesting the band splitting due to the exchange interaction within the itinerant Stoner model. Our results provide important insights into the electronic and magnetic properties of Fe5-xGeTe2 and the understanding of magnetism in a two-dimensional ferromagnetic system.
|
Mar 2022
|
|
I05-ARPES
|
Arindam
Pramanik
,
Ram Prakash
Pandeya
,
Denis V.
Vyalikh
,
Alexander
Generalov
,
Paolo
Moras
,
Asish K.
Kundu
,
Polina M.
Sheverdyaeva
,
Carlo
Carbone
,
Bhanu
Joshi
,
Arumugam
Thamizhavel
,
Srinivasan
Ramakrishnan
,
Kalobaran
Maiti
Diamond Proposal Number(s):
[11512]
Open Access
Abstract: BiPd is a noncentrosymmetric superconductor with Dirac-like surface states on both (010) and $\[(0\bar 10)\]$ faces. The Dirac cone on (010) surface is intense and appears at 0.66 eV binding energy. These states have drawn much attention due to contradictory reports on dimensionality and the momentum of these Dirac fermions. We have studied the properties of these Dirac fermions using varied photon energies and different experimental conditions. The behavior of the Dirac cone is found to be two-dimensional. In addition, we found few more surface states appearing at higher binding energies compared to the Dirac cone.
|
Mar 2022
|
|
I05-ARPES
|
Diamond Proposal Number(s):
[16871, 17192]
Open Access
Abstract: Spatial inhomogeneity on the electronic structure is one of the vital keys to provide a better understanding of the emergent quantum phenomenon. Given the recent developments on spatially resolved ARPES (ARPES: angle-resolved photoemission spectroscopy), the information on the spatial inhomogeneity on the local electronic structure is now accessible. However, the next challenge becomes apparent as the conventional analysis encounters difficulty handling a large volume of a spatial mapping dataset, typically generated in the spatially resolved ARPES experiments. Here, we propose a machine-learning-based approach using unsupervised clustering algorithms (K-means and fuzzy-c-means) to examine the spatial mapping dataset. Our analysis methods enable automated categorization of the spatial mapping dataset with a much-reduced human intervention and workload, thereby allowing quick identification and visualization of the spatial inhomogeneity on the local electronic structures.
|
Feb 2022
|
|
I05-ARPES
|
Georg
Poelchen
,
Igor P.
Rusinov
,
Susanne
Schulz
,
Monika
Guttler
,
Max
Mende
,
Alexander
Generalov
,
Dmitry Yu.
Usachov
,
Steffen
Danzenbacher
,
Johannes
Hellwig
,
Marius
Peters
,
Kristin
Kliemt
,
Yuri
Kucherenko
,
Victor N.
Antonov
,
Clemens
Laubschat
,
Evgueni V.
Chulkov
,
Arthur
Ernst
,
Kurt
Kummer
,
Cornelius
Krellner
,
Denis V.
Vyalikh
Diamond Proposal Number(s):
[24339]
Abstract: The f-driven temperature scales at the surfaces of strongly correlated materials have increasingly come into the focus of research efforts. Here, we unveil the emergence of a two-dimensional Ce Kondo lattice, which couples ferromagnetically to the ordered Co lattice below the P-terminated surface of the antiferromagnet CeCo2P2. In its bulk, Ce is passive and behaves tetravalently. However, because of symmetry breaking and an effective magnetic field caused by an uncompensated ferromagnetic Co layer, the Ce 4f states become partially occupied and spin-polarized near the surface. The momentum-resolved photoemission measurements indicate a strong admixture of the Ce 4f states to the itinerant bands near the Fermi level including surface states that are split by exchange interaction with Co. The temperature-dependent measurements reveal strong changes of the 4f intensity at the Fermi level in accordance with the Kondo scenario. Our findings show how rich and diverse the f-driven properties can be at the surface of materials without f-physics in the bulk.
|
Feb 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
|
D. F.
Liu
,
E. K.
Liu
,
Q. N.
Xu
,
J. L.
Shen
,
Y. W.
Li
,
D.
Pei
,
A. J.
Liang
,
P.
Dudin
,
T. K.
Kim
,
C.
Cacho
,
Y. F.
Xu
,
Y.
Sun
,
L. X.
Yang
,
Z. K.
Liu
,
C.
Felser
,
S. S. P.
Parkin
,
Y. L.
Chen
Open Access
Abstract: The spin–orbit coupling (SOC) lifts the band degeneracy that plays a vital role in the search for different topological states, such as topological insulators (TIs) and topological semimetals (TSMs). In TSMs, the SOC can partially gap a degenerate nodal line, leading to the formation of Dirac/Weyl semimetals (DSMs/WSMs). However, such SOC-induced gap structure along the nodal line in TSMs has not yet been systematically investigated experimentally. Here, we report a direct observation of such gap structure in a magnetic WSM Co3Sn2S2 using high-resolution angle-resolved photoemission spectroscopy. Our results not only reveal the existence and importance of the strong SOC effect in the formation of the WSM phase in Co3Sn2S2, but also provide insights for the understanding of its exotic physical properties.
|
Jan 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
|
|