606 research outputs found
The 6D quantum Hall effect and 3D topological pumps
Modern technological advances allow for the study of systems with additional
synthetic dimensions. Using such approaches, higher-dimensional physics that
was previously deemed to be of purely theoretical interest has now become an
active field of research. In this work, we derive from first principles using a
semiclassical equation of motions approach, the bulk response of a
six-dimensional Chern insulator. We find that in such a system a quantized bulk
response appears with a quantization originating from a six-dimensional
topological index -- the 3rd Chern number. Alongside this novel six-dimensional
response, we rigorously describe the lower even-dimensional Chern-like
responses that can occur due to nonvanishing 1st and 2nd Chern numbers in
sub-spaces of the six-dimensional space. Last, we propose how to realize such a
bulk response using three-dimensional topological charge pumps in cold atomic
systems.Comment: 12 pages + 13 pages of supporting material, 2 figures, published
versio
Topological Equivalence between the Fibonacci Quasicrystal and the Harper Model
One-dimensional quasiperiodic systems, such as the Harper model and the
Fibonacci quasicrystal, have long been the focus of extensive theoretical and
experimental research. Recently, the Harper model was found to be topologically
nontrivial. Here, we derive a general model that embodies a continuous
deformation between these seemingly unrelated models. We show that this
deformation does not close any bulk gaps, and thus prove that these models are
in fact topologically equivalent. Remarkably, they are equivalent regardless of
whether the quasiperiodicity appears as an on-site or hopping modulation. This
proves that these different models share the same boundary phenomena and
explains past measurements. We generalize this equivalence to any
Fibonacci-like quasicrystal, i.e., a cut and project in any irrational angle.Comment: 7 pages, 2 figures, minor change
Preferences in traumatic intracranial hemorrhage: bleeding vs. clotting
Patients with traumatic brain injury and resultant intracranial hemorrhage (ICH) are at high risk for developing venous thromboembolism (VTE). The use of thromboprophylaxis is effective at decreasing the rate of VTE, but at the potential expense of an increased risk of ICH progression. Physicians must carefully consider both the benefits and risks of VTE prophylaxis before prescribing chemical anticoagulants to these patients. To help clarify this difficult choice, Scales and colleagues performed a decision analysis to determine whether the benefits of thromboprophylaxis outweigh the potential risk of worsening ICH. There is increasing evidence that bleeding risks are not as prominent as previously thought. Although the results were largely inconclusive, the present study has identified areas for future research
Topological Photonics
Topological photonics is a rapidly emerging field of research in which
geometrical and topological ideas are exploited to design and control the
behavior of light. Drawing inspiration from the discovery of the quantum Hall
effects and topological insulators in condensed matter, recent advances have
shown how to engineer analogous effects also for photons, leading to remarkable
phenomena such as the robust unidirectional propagation of light, which hold
great promise for applications. Thanks to the flexibility and diversity of
photonics systems, this field is also opening up new opportunities to realize
exotic topological models and to probe and exploit topological effects in new
ways. This article reviews experimental and theoretical developments in
topological photonics across a wide range of experimental platforms, including
photonic crystals, waveguides, metamaterials, cavities, optomechanics, silicon
photonics, and circuit QED. A discussion of how changing the dimensionality and
symmetries of photonics systems has allowed for the realization of different
topological phases is offered, and progress in understanding the interplay of
topology with non-Hermitian effects, such as dissipation, is reviewed. As an
exciting perspective, topological photonics can be combined with optical
nonlinearities, leading toward new collective phenomena and novel strongly
correlated states of light, such as an analog of the fractional quantum Hall
effect.Comment: 87 pages, 30 figures, published versio
Hanbury-Brown and Twiss interference of anyons
We present a study of an Hanbury Brown and Twiss (HBT) interferometer
realized with anyons. Such a device can directly probe entanglement and
fractional statistics of initially uncorrelated particles. We calculate HBT
cross-correlations of Abelian Laughlin anyons. The correlations we calculate
exhibit partial bunching similar to bosons, indicating a substantial
statistical transmuta- tion from the underlying electronic degrees of freedom.
We also find qualitative differences between the anyonic signal and the
corresponding bosonic or fermionic signals, indicating that anyons cannot be
simply thought as intermediate between bosons and fermions.Comment: Refs adde
- …