16,488 research outputs found
Optical interface states protected by synthetic Weyl points
Weyl fermions have not been found in nature as elementary particles, but they
emerge as nodal points in the band structure of electronic and classical wave
crystals. Novel phenomena such as Fermi arcs and chiral anomaly have fueled the
interest in these topological points which are frequently perceived as
monopoles in momentum space. Here we report the experimental observation of
generalized optical Weyl points inside the parameter space of a photonic
crystal with a specially designed four-layer unit cell. The reflection at the
surface of a truncated photonic crystal exhibits phase vortexes due to the
synthetic Weyl points, which in turn guarantees the existence of interface
states between photonic crystals and any reflecting substrates. The reflection
phase vortexes have been confirmed for the first time in our experiments which
serve as an experimental signature of the generalized Weyl points. The
existence of these interface states is protected by the topological properties
of the Weyl points and the trajectories of these states in the parameter space
resembles those of Weyl semimetal "Fermi arcs surface states" in momentum
space. Tracing the origin of interface states to the topological character of
the parameter space paves the way for a rational design of strongly localized
states with enhanced local field.Comment: 36 pages, 9 figures. arXiv admin note: text overlap with
arXiv:1610.0434
Self-Learning Determinantal Quantum Monte Carlo Method
Self-learning Monte Carlo method [arXiv:1610.03137, 1611.09364] is a powerful
general-purpose numerical method recently introduced to simulate many-body
systems. In this work, we implement this method in the framework of
determinantal quantum Monte Carlo simulation of interacting fermion systems.
Guided by a self-learned bosonic effective action, our method uses a cumulative
update [arXiv:1611.09364] algorithm to sample auxiliary field configurations
quickly and efficiently. We demonstrate that self-learning determinantal Monte
Carlo method can reduce the auto-correlation time to as short as one near a
critical point, leading to -fold speedup. This enables to
simulate interacting fermion system on a lattice for the first
time, and obtain critical exponents with high accuracy.Comment: 5 pages, 4 figure
Applications of Bound States in the Continuum in Photonics
The intriguing properties of bound states in the continuum (BICs) have
attracted a lot of attention in photonics. Besides being effective in confining
light in a counter-intuitive way, the correspondence between the near-field
mode pattern and the far-field radiation of BICs manifests the fascinating
topological characteristics of light. Early works on photonic BICs were mainly
focused on designing artificial structures to facilitate their realization,
while recent advances have shifted to exploring their exceptional properties in
applications. In this review, we survey important breakthroughs and recent
advances in this field. We detail the unique properties of BICs, including
light confinement enhancement, sharp Fano resonances, and topological
characteristics. We provide insights into the unique phenomena derived from
BICs and the impact of BICs on various applications. We also discuss the
paradigm shift enabled or facilitated by BICs in several emerging research
frontiers, such as parity-time symmetric systems, higher-order topology,
exciton-photon coupling, and moir\'e superlattices
- …