118 research outputs found
Strain-induced pseudomagnetic field and Landau levels in photonic structures
Magnetic effects at optical frequencies are notoriously weak. This is
evidenced by the fact that the magnetic permeability of nearly all materials is
unity in the optical frequency range, and that magneto-optical devices (such as
Faraday isolators) must be large in order to allow for a sufficiently strong
effect. In graphene, however, it has been shown that inhomogeneous strains can
induce 'pseudomagnetic fields' that behave very similarly to real fields. Here,
we show experimentally and theoretically that, by properly structuring a
dielectric lattice, it is possible to induce a pseudomagnetic field at optical
frequencies in a photonic lattice, where the propagation dynamics is equivalent
to the evolution of an electronic wavepacket in graphene. To our knowledge,
this is the first realization of a pseudomagnetic field in optics. The induced
field gives rise to multiple photonic Landau levels (singularities in the
density of states) separated by band gaps. We show experimentally and
numerically that the gaps between these Landau levels give rise to transverse
confinement of the optical modes. The use of strain allows for the exploration
of magnetic effects in a non-resonant way that would be otherwise inaccessible
in optics. Employing inhomogeneous strain to induce pseudomagnetism suggests
the possibility that aperiodic photonic crystal structures can achieve greater
field-enhancement and slow-light effects than periodic structures via the high
density-of-states at Landau levels. Generalizing these concepts to other
systems beyond optics, for example with matter waves in optical potentials,
offers new intriguing physics that is fundamentally different from that in
purely periodic structures.Comment: 24 pages including supplementary information section, 4 figure
Topological Photonics
Topology is revolutionizing photonics, bringing with it new theoretical
discoveries and a wealth of potential applications. This field was inspired by
the discovery of topological insulators, in which interfacial electrons
transport without dissipation even in the presence of impurities. Similarly,
new optical mirrors of different wave-vector space topologies have been
constructed to support new states of light propagating at their interfaces.
These novel waveguides allow light to flow around large imperfections without
back-reflection. The present review explains the underlying principles and
highlights the major findings in photonic crystals, coupled resonators,
metamaterials and quasicrystals.Comment: progress and review of an emerging field, 12 pages, 6 figures and 1
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Relativistic quantum effects of Dirac particles simulated by ultracold atoms
Quantum simulation is a powerful tool to study a variety of problems in
physics, ranging from high-energy physics to condensed-matter physics. In this
article, we review the recent theoretical and experimental progress in quantum
simulation of Dirac equation with tunable parameters by using ultracold neutral
atoms trapped in optical lattices or subject to light-induced synthetic gauge
fields. The effective theories for the quasiparticles become relativistic under
certain conditions in these systems, making them ideal platforms for studying
the exotic relativistic effects. We focus on the realization of one, two, and
three dimensional Dirac equations as well as the detection of some relativistic
effects, including particularly the well-known Zitterbewegung effect and Klein
tunneling. The realization of quantum anomalous Hall effects is also briefly
discussed.Comment: 22 pages, review article in Frontiers of Physics: Proceedings on
Quantum Dynamics of Ultracold Atom
Interdependence between transportation system and power distribution system: a comprehensive review on models and applications
The rapidly increasing penetration of electric vehicles in modern metropolises has been witnessed during the past decade, inspired by financial subsidies as well as public awareness of climate change and environment protection. Integrating charging facilities, especially high-power chargers in fast charging stations, into power distribution systems remarkably alters the traditional load flow pattern, and thus imposes great challenges on the operation of distribution network in which controllable resources are rare. On the other hand, provided with appropriate incentives, the energy storage capability of electric vehicle offers a unique opportunity to facilitate the integration of distributed wind and solar power generation into power distribution system. The above trends call for thorough investigation and research on the interdependence between transportation system and power distribution system. This paper conducts a comprehensive survey on this line of research. The basic models of transportation system and power distribution system are introduced, especially the user equilibrium model, which describes the vehicular flow on each road segment and is not familiar to the readers in power system community. The modelling of interdependence across the two systems is highlighted. Taking into account such interdependence, applications ranging from long-term planning to short-term operation are reviewed with emphasis on comparing the description of traffic-power interdependence. Finally, an outlook of prospective directions and key technologies in future research is summarized.fi=vertaisarvioitu|en=peerReviewed
The ATLAS Trigger/DAQ Authorlist, version 1.0
This is a reference document giving the ATLAS Trigger/DAQ author list, version 1.0 of 20 Nov 2008
The ATLAS trigger - high-level trigger commissioning and operation during early data taking
The ATLAS experiment is one of the two general-purpose experiments due to start operation soon at the Large Hadron Collider (LHC). The LHC will collide protons at a centre of mass energy of 14~TeV, with a bunch-crossing rate of 40~MHz. The ATLAS three-level trigger will reduce this input rate to match the foreseen offline storage capability of 100-200~Hz. This paper gives an overview of the ATLAS High Level Trigger focusing on the system design and its innovative features. We then present the ATLAS trigger strategy for the initial phase of LHC exploitation. Finally, we report on the valuable experience acquired through in-situ commissioning of the system where simulated events were used to exercise the trigger chain. In particular we show critical quantities such as event processing times, measured in a large-scale HLT farm using a complex trigger menu
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