15 research outputs found
Experimental observation of hidden Berry curvature in inversion-symmetric bulk 2H-WSe2
We investigate the hidden Berry curvature in bulk 2H-WSe2 by utilizing the
surface sensitivity of angle resolved photoemission (ARPES). The symmetry in
the electronic structure of transition metal dichalcogenides is used to
uniquely determine the local orbital angular momentum (OAM) contribution to the
circular dichroism (CD) in ARPES. The extracted CD signals for the K and K'
valleys are almost identical but their signs, which should be determined by the
valley index, are opposite. In addition, the sign is found to be the same for
the two spin-split bands, indicating that it is independent of spin state.
These observed CD behaviors are what are expected from Berry curvature of a
monolayer of WSe2. In order to see if CD-ARPES is indeed representative of
hidden Berry curvature within a layer, we use tight binding analysis as well as
density functional calculation to calculate the Berry curvature and local OAM
of a monolayer WSe2. We find that measured CD-ARPES is approximately
proportional to the calculated Berry curvature as well as local OAM, further
supporting our interpretation.Comment: 6 pages, 3 figure
Deep learning-based statistical noise reduction for multidimensional spectral data
In spectroscopic experiments, data acquisition in multi-dimensional phase
space may require long acquisition time, owing to the large phase space volume
to be covered. In such case, the limited time available for data acquisition
can be a serious constraint for experiments in which multidimensional spectral
data are acquired. Here, taking angle-resolved photoemission spectroscopy
(ARPES) as an example, we demonstrate a denoising method that utilizes deep
learning as an intelligent way to overcome the constraint. With readily
available ARPES data and random generation of training data set, we
successfully trained the denoising neural network without overfitting. The
denoising neural network can remove the noise in the data while preserving its
intrinsic information. We show that the denoising neural network allows us to
perform similar level of second-derivative and line shape analysis on data
taken with two orders of magnitude less acquisition time. The importance of our
method lies in its applicability to any multidimensional spectral data that are
susceptible to statistical noise.Comment: 8 pages, 8 figure
Electronic band structure of (111) thin filman angle-resolved photoemission spectroscopy study
We studied the electronic band structure of pulsed laser deposition (PLD)
grown (111)-oriented SrRuO (SRO) thin films using \textit{in situ}
angle-resolved photoemission spectroscopy (ARPES) technique. We observed
previously unreported, light bands with a renormalized quasiparticle effective
mass of about 0.8. The electron-phonon coupling underlying this mass
renormalization yields a characteristic "kink" in the band dispersion. The
self-energy analysis using the Einstein model suggests five optical phonon
modes covering an energy range 44 to 90 meV contribute to the coupling.
Besides, we show that the quasiparticle spectral intensity at the Fermi level
is considerably suppressed, and two prominent peaks appear in the valance band
spectrum at binding energies of 0.8 eV and 1.4 eV, respectively. We discuss the
possible implications of these observations. Overall, our work demonstrates
that high-quality thin films of oxides with large spin-orbit coupling can be
grown along the polar (111) orientation by the PLD technique, enabling
\textit{in situ} electronic band structure study. This could allow for
characterizing the thickness-dependent evolution of band structure of (111)
heterostructuresa prerequisite for exploring possible topological quantum
states in the bilayer limit
Understanding the Role of Electronic Effects in CO on the Pt-Sn Alloy Surface via Band Structure Measurements
Using angle-resolved photoemission spectroscopy, we show direct evidence for charge transfer between adsorbed molecules and metal substrates, i.e., chemisorption of CO on Pt(111) and Pt-Sn/Pt(111) 2 x 2 surfaces. The observed band structures show a unique signature of charge transfer as CO atoms are adsorbed, revealing the roles of specific orbital characters participating in the chemisorption process. As the coverage of CO increases, the degree of charge transfer between CO and Pt shows a clear difference to that of Pt-Sn. With comparison to density functional theory calculation results, the observed distinct features in the band structure are interpreted as back-donation bonding states formed between the Pt molecular orbital and the 2 pi orbital of CO. Furthermore, the change in the surface charge concentration, measured from the Fermi surface area, shows that the Pt surface has a larger charge concentration change than the Pt-Sn surface upon CO adsorption. The differences between Pt and Pt-Sn surfaces are due to the effect of Pt-Sn intermetallic bonding on the interaction of CO with the surface
Electronic structures of CO adsorbed Pt-skin surface on Pt–Co and Pt–Ni alloys
© 2021 Korean Physical SocietyBy using angle resolved photoemission spectroscopy, we investigate the electronic structures of Pt-skin layer of Pt–Co and Pt–Ni alloys with CO molecules on the surface. Measured Fermi surface maps and band dispersions reflect the signatures of chemical bonding between Pt-skin layer and CO molecules. Furthermore, the degree of chemical bonding strength of CO molecules, estimated from the energy shift of the participating bands, is found to be reduced on both Pt bimetallic alloys. Our results show how the surface band structure of Pt bimetallic alloys is modified with molecular orbitals of CO molecules on the surface, revealing the important role of the electronic structure in the determination of chemical properties of bimetallic alloys.11Nsciescopuskc
Universality of charge doping driven metal-insulator transition in Sr2RhO4 and role of spin-orbit coupling
We performed angle-resolved photoemission spectroscopy (ARPES) experiments on an electron-doped Sr2RhO4 system Sr2-xCexRhO4 in order to investigate the electron doping-induced metal-insulator transition (MIT). We establish the universality of MIT in electron-doped Sr2RhO4 by comparing results from Sr2-xLaxRhO4 and Sr2-xCexRhO4. Via a systematic analysis of doping-dependent transport and ARPES data, we show that the correlation driven MIT with a noninteger electron number in electron-doped Sr2RhO4 is universal and thus independent of the dopant. Within the universality, the ARPES analysis shows that the band topology determined by the spin-orbit coupling (SOC) is likely a control parameter of the insulating gap size and critical electron number of the MIT. We present a phase diagram of the insulating phase as a function of the effective SOC and electron number. © 2022 American Physical Society.11Nsciescopu
Additional file 1: Figure S1. of Gene-gene interaction analysis identifies a new genetic risk factor for colorectal cancer
Overall study population design. (TIFF 1061Â kb
Additional file 2: Figure S2. of Gene-gene interaction analysis identifies a new genetic risk factor for colorectal cancer
Linkage disequilibrium of six SNPs of the adiponectin gene (APN). (TIFF 599Â kb
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Experimental Observation of Hidden Berry Curvature in Inversion-Symmetric Bulk 2H-WSe_{2}.
We investigate the hidden Berry curvature in bulk 2H-WSe_{2} by utilizing the surface sensitivity of angle resolved photoemission (ARPES). The symmetry in the electronic structure of transition metal dichalcogenides is used to uniquely determine the local orbital angular momentum (OAM) contribution to the circular dichroism (CD) in ARPES. The extracted CD signals for the K and K^{'} valleys are almost identical, but their signs, which should be determined by the valley index, are opposite. In addition, the sign is found to be the same for the two spin-split bands, indicating that it is independent of spin state. These observed CD behaviors are what are expected from Berry curvature of a monolayer of WSe_{2}. In order to see if CD-ARPES is indeed representative of hidden Berry curvature within a layer, we use tight binding analysis as well as density functional calculation to calculate the Berry curvature and local OAM of a monolayer WSe_{2}. We find that measured CD-ARPES is approximately proportional to the calculated Berry curvature as well as local OAM, further supporting our interpretation