1,122 research outputs found
Dirac dispersion and non-trivial Berry's phase in three-dimensional semimetal RhSb3
We report observations of magnetoresistance, quantum oscillations and
angle-resolved photoemission in RhSb, a unfilled skutterudite semimetal
with low carrier density. The calculated electronic band structure of RhSb
entails a quantum number in analogy to
strong topological insulators, and inverted linear valence/conduction bands
that touch at discrete points close to the Fermi level, in agreement with
angle-resolved photoemission results. Transport experiments reveal an
unsaturated linear magnetoresistance that approaches a factor of 200 at 60 T
magnetic fields, and quantum oscillations observable up to 150~K that are
consistent with a large Fermi velocity ( ms), high
carrier mobility ( /Vs), and small three dimensional hole pockets
with nontrivial Berry phase. A very small, sample-dependent effective mass that
falls as low as bare masses scales with Fermi velocity, suggesting
RhSb is a new class of zero-gap three-dimensional Dirac semimetal.Comment: 9 pages, 4 figure
The electronic structure of the high-symmetry perovskite iridate Ba2IrO4
We report angle-resolved photoemission (ARPES) measurements, density
functional and model tight-binding calculations on BaIrO (Ba-214), an
antiferromagnetic ( K) insulator. Ba-214 does not exhibit the
rotational distortion of the IrO octahedra that is present in its sister
compound SrIrO (Sr-214), and is therefore an attractive reference
material to study the electronic structure of layered iridates. We find that
the band structures of Ba-214 and Sr-214 are qualitatively similar, hinting at
the predominant role of the spin-orbit interaction in these materials.
Temperature-dependent ARPES data show that the energy gap persists well above
, and favour a Mott over a Slater scenario for this compound.Comment: 13 pages, 9 figure
Topological surface states above the Fermi energy in
We report a detailed experimental study of the band structure of the recently
discovered topological material . Using
the combination of scanning tunneling spectroscopy and angle-resolved
photo-emission spectroscopy with surface K-doping, we probe the band structure
of with energy and momentum resolution
above the Fermi level. Our experiments show the presence of multiple surface
states with a linear Dirac-like dispersion, consistent with the predictions
from previously reported band structure calculations. In particular, scanning
tunneling spectroscopy measurements provide the first experimental evidence for
the strong topological surface state predicted at 460 meV, which stems from the
band inversion between Hf-d and Te-p orbitals. This band inversion comprised of
more localized d-states could result in a better surface-to-bulk conductance
ratio relative to more traditional topological insulators.Comment: Supplementary materials available upon reques
Tunable Polaronic Conduction in Anatase TiO2
Oxygen vacancies created in anatase TiO2 by UV photons (80–130 eV) provide an effective electron-doping mechanism and induce a hitherto unobserved dispersive metallic state. Angle resolved photoemission reveals that the quasiparticles are large polarons. These results indicate that anatase can be tuned from an insulator to a polaron gas to a weakly correlated metal as a function of doping and clarify the nature of conductivity in this material.open1192sciescopu
Persistence of metabolic monitoring for psychiatry inpatients treated with second‐generation antipsychotics utilizing a computer‐based intervention
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/135222/1/jcpt12368.pd
Anderson Transition in Disordered Graphene
We use the regularized kernel polynomial method (RKPM) to numerically study
the effect disorder on a single layer of graphene. This accurate numerical
method enables us to study very large lattices with millions of sites, and
hence is almost free of finite size errors. Within this approach, both weak and
strong disorder regimes are handled on the same footing. We study the
tight-binding model with on-site disorder, on the honeycomb lattice. We find
that in the weak disorder regime, the Dirac fermions remain extended and their
velocities decrease as the disorder strength is increased. However, if the
disorder is strong enough, there will be a {\em mobility edge} separating {\em
localized states around the Fermi point}, from the remaining extended states.
This is in contrast to the scaling theory of localization which predicts that
all states are localized in two-dimensions (2D).Comment: 4 page
Direct observation of minibands in twisted heterobilayers
Stacking two-dimensional (2D) van der Waals materials with different
interlayer atomic registry in a heterobilayer causes the formation of a
long-range periodic superlattice that may bestow the heterostructure with
exotic properties such as new quantum fractal states [1-3] or superconductivity
[4, 5]. Recent optical measurements of transition metal dichalcogenide (TMD)
heterobilayers have revealed the presence of hybridized interlayer
electron-hole pair excitations at energies defined by the superlattice
potential [6-10]. The corresponding quasiparticle band structure, so-called
minibands, have remained elusive and no such features have been reported for
heterobilayers comprised of a TMD and another type of 2D material. Here, we
introduce a new X-ray capillary technology for performing micro-focused
angle-resolved photoemission spectroscopy (microARPES) with a spatial
resolution on the order of 1 m, enabling us to map the momentum-dependent
quasiparticle dispersion of heterobilayers consisting of graphene on WS at
variable interlayer twist angles (). Minibands are directly observed
for in multiple mini Brillouin zones (mBZs), while they
are absent for a larger twist angle of . These findings
underline the possibility to control quantum states via the stacking
configuration in 2D heterostructures, opening multiple new avenues for
generating materials with enhanced functionality such as tunable electronic
correlations [11] and tailored selection rules for optical transitions [12].Comment: Main manuscript: 14 pages, 4 figures. Supporting information: 8
pages, 5 figure
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