114 research outputs found
Topology in quasicrystals
Topological phases of matter have sparked an immense amount of activity in
recent decades. Topological materials are classified by topological invariants
that act as a non-local order parameter for any symmetry and condition. As a
result, they exhibit quantized bulk and boundary observable phenomena,
motivating various applications that are robust to perturbations. In this
review, we explore such a topological classification for quasiperiodic systems,
and detail recent experimental activity in the field.Comment: 14 pages, 6 figures, contribution to feature issue "Photonic
Topological Materials" in Optical Materials Express, comments are welcom
Charge sensing amplification via weak values measurement
A protocol employing weak values (WVs) to obtain ultra sensitive
amplification of weak signals in the context of a solid state setup is
proposed. We consider an Aharonov-Bohm interferometer where both the orbital
and the spin degrees of freedom are weakly affected by the presence of an
external charge to be detected. The interplay between the spin and the orbital
WVs leads to a significant amplification even in the presence of finite
temperature, voltage, and external noise.Comment: 6 pages, 5 figure
Measuring cotunneling in its wake
We introduce a rate formalism to treat classically forbidden electron
transport through a quantum dot (cotunneling) in the presence of a coupled
measurement device. We demonstrate this formalism for a toy model case of
cotunneling through a single-level dot while being coupled to a strongly
pinched-off quantum point contact (QPC). We find that the detector generates
three types of back-action: the measurement collapses the coherent transport
through the virtual state, but at the same time allows for QPC-assisted
incoherent transport, and widens the dot level. Last, we obtain the measured
cotunneling time from the cross correlation between dot and QPC currents.Comment: 15 pages, 9 figures, 1 appendix, published versio
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
Fractional quantum Hall edge polaritons
It is commonly believed that light cannot couple to the collective
excitations of the fractional quantum Hall effect (FQHE). This assumption
relies on Kohn's theorem that states that electron-electron interactions
decouple from homogeneous electromagnetic fields due to Galilean invariance.
Here, we demonstrate that in finite systems light-matter coupling beyond the
dipole approximation breaks Kohn's theorem, and enables the coupling of cavity
photons to the plasmonic edge modes of the FQHE. We derive the coupling using
the FQHE bulk-boundary correspondence and predict the formation of
experimentally detectable plasmon polaritons. In conjunction with recent
experiments, we find that a single cavity mode leaves the system's topological
protection intact. Interestingly, however, a multimode cavity mediates plasmon
backscattering and effectively transforms the edges of the 2D FQHE into a 1D
wire. Such cavity-meditated nonlocal backscattering bodes the breakdown of the
topological protection in the regime of ultra-strong photon-plasmon coupling.
Our analytical framework and findings pave the way for investigating the
topological order of the FQHE via optical spectroscopic probes as well as
provide new opportunities to control FQHE edge excitations using light.Comment: 25 pages, 4 figure
High-order topological insulators from high-dimensional Chern insulators
Topological insulators are a novel state of matter that share a common
feature: their spectral bands are associated with a nonlocal integer-valued
index, commonly manifesting through quantized bulk phenomena and robust
boundary effects. In this work, we demonstrate using dimensional reduction that
high-order topological insulators are descendants from a chiral semimetal in
higher dimensions. Specifically, we analyze the descendants of an ancestor
four-dimensional Chern insulator in the limit where it becomes chiral and show
their relation to two-dimensional second-order topological insulators.
Correspondingly, the quantization of the charge accumulation at the corners of
the 2D descendants is obtained and related to the topological indices -- the
1st and 2nd Chern numbers -- of the ancestor model. Our approach provides a
connection between the boundary states of high-order topological insulators and
topological pumps -- the latter being dynamical realizations of
high-dimensional Chern insulators.Comment: 5 pages, 3 figures + supplementary material (8 pages), comments are
welcom
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