I06-Nanoscience (XPEEM)
|
Xinqi
Liu
,
Puyang
Huang
,
Yunyouyou
Xia
,
Lei
Gao
,
Liyang
Liao
,
Baoshan
Cui
,
Dirk
Backes
,
Gerrit
Van Der Laan
,
Thorsten
Hesjedal
,
Yuchen
Ji
,
Peng
Chen
,
Yifan
Zhang
,
Fan
Wu
,
Meixiao
Wang
,
Junwei
Zhang
,
Guoqiang
Yu
,
Cheng
Song
,
Yulin
Chen
,
Zhongkai
Liu
,
Yumeng
Yang
,
Yong
Peng
,
Gang
Li
,
Qi
Yao
,
Xufeng
Kou
Abstract: To harness the intriguing properties of 2D van der Waals (vdW) ferromagnets (FMs) for versatile applications, the key challenge lies in the reliable material synthesis for scalable device production. Here, the epitaxial growth of single-crystalline 1T-CrTe2 thin films on 2-inch sapphire substrates are demonstrated. Benefiting from the uniform surface energy of the dangling bond-free Al2O3(0001) surface, the layer-by-layer vdW growth mode is observed right from the initial growth stage, which warrants precise control of the sample thickness beyond three monolayer and homogeneous surface morphology across the entire wafer. Moreover, the presence of the Coulomb interaction at the CrTe2/Al2O3 interface plays an important role in tailoring the anomalous Hall response, and the structural optimization of the CrTe2-based spin-orbit torque device leads to a substantial switching power reduction by 54%. The results may lay out a general framework for the design of energy-efficient spintronics based on configurable vdW FMs.
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Sep 2023
|
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I05-ARPES
|
R. Z.
Xu
,
Xian
Du
,
J. S.
Zhou
,
X.
Gu
,
Q. Q.
Zhang
,
Y. D.
Li
,
W. X.
Zhao
,
F. W.
Zheng
,
M.
Arita
,
K.
Shimada
,
T. K.
Kim
,
C.
Cacho
,
Y. F.
Guo
,
Zhongkai
Liu
,
Y. L.
Chen
,
L. X.
Yang
Diamond Proposal Number(s):
[20683]
Open Access
Abstract: TaTe4, a metallic charge-density wave (CDW) material discovered decades ago, has attracted renewed attention due to its rich interesting properties, such as pressure-induced superconductivity and candidate nontrivial topological phase. Here, using high-resolution angle-resolved photoemission spectroscopy and ab initio calculation, we systematically investigate the electronic structure of TaTe4. At 26 K, we observe a CDW gap as large as 290 meV, which persists up to 500 K. The CDW-modulated band structure shows a complex reconstruction that closely correlates with the lattice distortion. Inside the CDW gap, there exist highly dispersive energy bands contributing to the remnant Fermi surface and metallic behavior in the CDW state. Interestingly, our ab initio calculation reveals that the large CDW gap mainly opens in the electronic states with out-of-plane orbital components, while the in-gap metallic states originate from in-plane orbitals, suggesting an orbital texture that couples with the CDW order. Our results shed light on the interplay between electron, lattice, and orbital in quasi-one-dimensional CDW materials.
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Aug 2023
|
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I05-ARPES
|
Q. Q.
Zhang
,
Y.
Shi
,
K. Y.
Zhai
,
W. X.
Zhao
,
X.
Du
,
J. S.
Zhou
,
X.
Gu
,
R. Z.
Xu
,
Y. D.
Li
,
Y. F.
Guo
,
Z. K.
Liu
,
C.
Chen
,
S.-K.
Mo
,
T. K.
Kim
,
C.
Cacho
,
J. W.
Yu
,
W.
Li
,
Y. L.
Chen
,
J.-H.
Chu
,
L. X.
Yang
Diamond Proposal Number(s):
[22375]
Abstract: EuTe
4
is a van der Waals material exhibiting a charge density wave (CDW) with a large thermal hysteresis in the resistivity and CDW gap. In this paper, we systematically study the electronic structure and transport properties of
EuTe
4
using high-resolution angle-resolved photoemission spectroscopy (ARPES), magnetoresistance (MR) measurements, and scanning tunneling microscopy (STM). We observe a CDW gap of
∼
200
meV
at low temperatures that persists up to 400 K, suggesting that the CDW transition occurs at a much higher temperature. The ARPES intensity near the Fermi level shows large thermal hysteretic behavior, consistent with the resistivity measurement. The hysteresis in the resistivity measurement does not change under a magnetic field up to 7 T, excluding the thermal magnetic hysteretic effect. Instead, the surface topography measured with STM shows surface domains with different CDW trimerization directions, which may be important for the thermal hysteretic behavior. Interestingly, we reveal a large negative MR at low temperatures that can be associated with the canting of magnetically ordered Eu spins. Our results shed light on the understanding of magnetic, transport, and electronic properties of
EuTe
4
.
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Mar 2023
|
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I05-ARPES
|
Haifeng
Yang
,
Jingjing
Gao
,
Yingying
Cao
,
Yuanji
Xu
,
Aiji
Liang
,
Xiang
Xu
,
Yujie
Chen
,
Shuai
Liu
,
Kui
Huang
,
Lixuan
Xu
,
Chengwei
Wang
,
Shengtao
Cui
,
Meixiao
Wang
,
Lexian
Yang
,
Xuan
Luo
,
Yuping
Sun
,
Yi-Feng
Yang
,
Zhongkai
Liu
,
Yulin
Chen
Open Access
Abstract: Mott physics plays a critical role in materials with strong electronic correlations. Mott insulator-to-metal transition can be driven by chemical doping, external pressure, temperature and gate voltage, which is often seen in transition metal oxides with 3d electrons near the Fermi energy (e.g. cuprate superconductor). In 4f-electron system, however, the insulator-to-metal transition is mostly driven by Kondo hybridization and the Mott physics has rarely been explored in experiments. Here, by combining the angle-resolved photoemission spectroscopy and strongly correlated band structure calculations, we show that an unusual Mott instability exists in YbInCu4 accompanying its mysterious first-order valence transition. This contrasts with the prevalent Kondo picture and demonstrates that YbInCu4 is a unique platform to explore the Mott physics in Kondo lattice systems. Our work provides important insight for the understanding and manipulation of correlated quantum phenomena in the f-electron system.
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Feb 2023
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I05-ARPES
|
Hongwei
Fang
,
Meng
Lyu
,
Hao
Su
,
Jian
Yuan
,
Yiwei
Li
,
Lixuan
Xu
,
Shuai
Liu
,
Liyang
Wei
,
Xinqi
Liu
,
Haifeng
Yang
,
Qi
Yao
,
Meixiao
Wang
,
Yanfeng
Guo
,
Wujun
Shi
,
Yulin
Chen
,
Enke
Liu
,
Zhongkai
Liu
Abstract: The kagome-lattice crystal hosts various intriguing properties including the frustrated magnetism, charge order, topological state, superconductivity and correlated phenomena. To achieve high-performance kagome-lattice compounds for electronic and spintronic applications, careful tuning of the band structure would be desired. Here, the electronic structures of kagome-lattice crystal Ni3In2S2 were investigated by transport measurements, angle-resolved photoemission spectroscopy as well as ab initio calculations. The transport measurements reveal Ni3In2S2 as a compensated semimetal with record-high carrier mobility (∼8683 and 7356 cm2 V−1 S−1 for holes and electrons) and extreme magnetoresistance (15,518% at 2 K and 13 T) among kagome-lattice materials. These extraordinary properties are well explained by its band structure with indirect gap, small electron/hole pockets and large bandwidth of the 3d electrons of Ni on the kagome lattice. This work demonstrates that the crystal field and doping serve as the key tuning knobs to optimize the transport properties in kagome-lattice crystals. Our work provides material basis and optimization routes for kagome-lattice semimetals towards electronics and spintronics applications.
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Feb 2023
|
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I05-ARPES
|
Xian
Du
,
L.
Kang
,
Y. Y.
Lv
,
J. S.
Zhou
,
X.
Gu
,
R. Z.
Xu
,
Q. Q.
Zhang
,
Z. X.
Yin
,
W. X.
Zhao
,
Y. D.
Li
,
S. M.
He
,
D.
Pei
,
Y. B.
Chen
,
M. X.
Wang
,
Z. K.
Liu
,
Y. L.
Chen
,
L. X.
Yang
Diamond Proposal Number(s):
[22375]
Abstract: Although the concept of the Luttinger liquid (LL) describing a one-dimensional (1D) interacting fermion system1,2 collapses at higher dimensions, it has been proposed to be relevant to enigmatic problems in condensed matter physics including the normal state of cuprate superconductors3,4,5, unconventional metals6,7 and quantum criticality8,9. Here we investigate the electronic structure of quasi-2D η-Mo4O11, a charge-density wave material, using high-resolution angle-resolved photoemission spectroscopy and ab initio calculations. We show a prototypical LL behaviour originating from the crossed quasi-1D chain arrays hidden in the quasi-2D crystal structure. Our results suggest that η-Mo4O11 materializes the crossed LL phase10,11,12 in its normal state, where the orthogonal orbital components substantially reduce the coupling between intersecting quasi-1D chains and therefore maintain the essential properties of the LL. Our finding not only presents a realization of a 2D LL, but also provides a new angle to understand non-Fermi liquid behaviour in other 2D and 3D quantum materials.
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Dec 2022
|
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I05-ARPES
|
Z. X.
Yin
,
X.
Du
,
S.
Zhang
,
C.
Chen
,
D.
Pei
,
J. S.
Zhou
,
X.
Gu
,
R. Z.
Xu
,
Q. Q.
Zhang
,
W. X.
Zhao
,
Y. D.
Li
,
Y. F.
Xu
,
A.
Bernevig
,
Z. K.
Liu
,
E. K.
Liu
,
Y. L.
Chen
,
L. X.
Yang
Diamond Proposal Number(s):
[24167]
Abstract: Recently, magnetic topological quantum materials have attracted substantial research attention due to their great application potential. Here, using high-resolution angle-resolved photoemission spectroscopy and ab initio calculation, we systematically investigate the electronic structure of antiferromagnet Dirac semimetal candidate
Gd
In
3
. According to our ab initio calculation, there exist two and one pair(s) of Dirac fermions in the paramagnetic and antiferromagnetic state, respectively. In the antiferromagnetic state, the magnetic Dirac semimetal phase is protected by
C
4
z
rotation symmetry in the type-IV magnetic space group. Our experiment above the Néel temperature is well reproduced by the calculated band structure in the paramagnetic state, from which we identify a pair of Dirac fermions at 1.5 eV below the Fermi level. However, we do not observe the signature of electronic reconstruction in the antiferromagnetic state, suggesting a weak interaction between the localized Gd
4
f
states of spin configuration
S
=
7
/
2
μ
B
and the itinerant conduction electrons. Our results confirm the Dirac semimetal nature of the paramagnetic
Gd
In
3
and provide important insights into its antiferromagnetic Dirac semimetal phase.
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Aug 2022
|
|
I06-Nanoscience (XPEEM)
|
X.
Gu
,
C.
Chen
,
W. S.
Wei
,
L. L.
Gao
,
J. Y.
Liu
,
X.
Du
,
D.
Pei
,
J. S.
Zhou
,
R. Z.
Xu
,
Z. X.
Yin
,
W. X.
Zhao
,
Y. D.
Li
,
C.
Jozwiak
,
A.
Bostwick
,
E.
Rotenberg
,
D.
Backes
,
L. S. I.
Veiga
,
S.
Dhesi
,
T.
Hesjedal
,
G.
Van Der Laan
,
H. F.
Du
,
W. J.
Jiang
,
Y. P.
Qi
,
G.
Li
,
W. J.
Shi
,
Z. K.
Liu
,
Y. L.
Chen
,
L. X.
Yang
Diamond Proposal Number(s):
[27482]
Abstract: Crystal geometry can greatly influence the emergent properties of quantum materials. As an example, the kagome lattice is an ideal platform to study the rich interplay between topology, magnetism, and electronic correlation. In this work, combining high-resolution angle-resolved photoemission spectroscopy and ab initio calculation, we systematically investigate the electronic structure of
X
Mn
6
Sn
6
(
X
=
Dy
,
Tb
,
Gd
,
Y
)
family compounds. We observe the Dirac fermion and the flat band arising from the magnetic kagome lattice of Mn atoms. Interestingly, the flat band locates in the same energy region in all compounds studied, regardless of their different magnetic ground states and
4
f
electronic configurations. These observations suggest a robust Mn magnetic kagome lattice across the
X
Mn
6
Sn
6
family, thus providing an ideal platform for the search for, and investigation of, new emergent phenomena in magnetic topological materials.
|
Apr 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
|
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
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