304 research outputs found
Buried double CuO chains in YBaCuO uncovered by nano-ARPES
The electron dynamics in the CuO chains has been elusive in Y-Ba-Cu-O cuprate
systems by means of standard angle-resolved photoemission spectroscopy (ARPES);
cleaved sample exhibits areas terminated by both CuO-chain or BaO layers, and
the size of a typical beam results in ARPES signals that are superposed from
both terminations. Here, we employ spatially-resolved ARPES with submicrometric
beam (nano-ARPES) to reveal the surface-termination-dependent electronic
structures of the double CuO chains in YBaCuO. We present the first
observation of sharp metallic dispersions and Fermi surfaces of the double CuO
chains buried underneath the CuO-plane block on the BaO terminated surface.
While the observed Fermi surfaces of the CuO chains are highly one-dimensional,
the electrons in the CuO-chains do not undergo significant electron
correlations and no signature of a Tomonaga-Luttinger liquid nor a marginal
Fermi liquid is found. Our works represent an important experimental step
toward understanding of the charge dynamics and provides a starting basis for
modelling the high- superconductivity in YBCO cuprate systems.Comment: 10 pages, 5 figures including supplementary material (4 pages, 2
figures
Momentum Dependence of Charge Excitations in the Electron-Doped Superconductor Nd1.85Ce0.15CuO4: a RIXS Study
We report a resonant inelastic x-ray scattering (RIXS) study of charge
excitations in the electron-doped high-Tc superconductor Nd1.85Ce0.15CuO4. The
intraband and interband excitations across the Fermi energy are separated for
the first time by tuning the experimental conditions properly to measure charge
excitations at low energy. A dispersion relation with q-dependent width emerges
clearly in the intraband excitation, while the intensity of the interband
excitation is concentrated around 2 eV near the zone center. The experimental
results are consistent with theoretical calculation of the RIXS spectra based
on the Hubbard model
Towards green business process management
There is a global consensus on the need to reduce our collective carbon footprint. While much research attention has focused on developing alternative energy sources, automotive technologies or waste disposal techniques, we often ignore the fact that the ability to optimize (existing) operations to reduce their emissions impact is fundamental to this exercise. We believe that by transforming the problem into the domain of Business Process Management (BPM) we can leverage the rich expertise in this field to address issues associated with identifying areas for improvement, understanding the implication and performing carbon footprint minimization. We will use the term “Green BPM” to describe a novel class of technologies that leverage and extend existing BPM technology to enable process design, analysis, execution and monitoring in a manner informed by the carbon footprint of process designs and instances. This article describes the first steps in the development of this class of technologies
Control of a two-dimensional electron gas on SrTiO3(111) by atomic oxygen
We report on the formation of a two-dimensional electron gas (2DEG) at the
bare surface of (111) oriented SrTiO3. Angle resolved photoemission experiments
reveal highly itinerant carriers with a 6-fold symmetric Fermi surface and
strongly anisotropic effective masses. The electronic structure of the 2DEG is
in good agreement with self-consistent tight-binding supercell calculations
that incorporate a confinement potential due to surface band bending. We
further demonstrate that alternate exposure of the surface to ultraviolet light
and atomic oxygen allows tuning of the carrier density and the complete
suppression of the 2DEG.Comment: 5 pages, 4 figure
Understanding the complex phase diagram of uranium: the role of electron-phonon coupling
We report an experimental determination of the dispersion of the soft phonon
mode along [1,0,0] in uranium as a function of pressure. The energies of these
phonons increase rapidly, with conventional behavior found by 20 GPa, as
predicted by recent theory. New calculations demonstrate the strong pressure
(and momentum) dependence of the electron-phonon coupling, whereas the
Fermi-surface nesting is surprisingly independent of pressure. This allows a
full understanding of the complex phase diagram of uranium, and the interplay
between the charge-density wave and superconductivity
Electronic structure of the candidate 2D Dirac semimetal SrMnSb2: a combined experimental and theoretical study
SrMnSb is suggested to be a magnetic topological semimetal. It contains
square, 2D Sb planes with non-symmorphic crystal symmetries that could protect
band crossings, offering the possibility of a quasi-2D, robust Dirac semi-metal
in the form of a stable, bulk (3D) crystal. Here, we report a combined and
comprehensive experimental and theoretical investigation of the electronic
structure of SrMnSb, including the first ARPES data on this compound.
SrMnSb possesses a small Fermi surface originating from highly 2D, sharp
and linearly dispersing bands (the Y-states) around the (0,/a)-point in
-space. The ARPES Fermi surface agrees perfectly with that from
bulk-sensitive Shubnikov de Haas data from the same crystals, proving the
Ystates to be responsible for electrical conductivity in SrMnSb. DFT and
tight binding (TB) methods are used to model the electronic states, and both
show good agreement with the ARPES data. Despite the great promise of the
latter, both theory approaches show the Y-states to be gapped above E,
suggesting trivial topology. Subsequent analysis within both theory approaches
shows the Berry phase to be zero, indicating the non-topological character of
the transport in SrMnSb, a conclusion backed up by the analysis of the
quantum oscillation data from our crystals.Comment: 26 pages, 10 figures, revised submission to SciPost after including
changes requested by referees. All referee reports are open and can be viewed
here: https://scipost.org/submissions/1711.07165v2
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