5,459 research outputs found
Quantum Transport Simulation of III-V TFETs with Reduced-Order K.P Method
III-V tunneling field-effect transistors (TFETs) offer great potentials in
future low-power electronics application due to their steep subthreshold slope
and large "on" current. Their 3D quantum transport study using non-equilibrium
Green's function method is computationally very intensive, in particular when
combined with multiband approaches such as the eight-band K.P method. To reduce
the numerical cost, an efficient reduced-order method is developed in this
article and applied to study homojunction InAs and heterojunction GaSb-InAs
nanowire TFETs. Device performances are obtained for various channel widths,
channel lengths, crystal orientations, doping densities, source pocket lengths,
and strain conditions
Zero-Shot Visual Recognition using Semantics-Preserving Adversarial Embedding Networks
We propose a novel framework called Semantics-Preserving Adversarial
Embedding Network (SP-AEN) for zero-shot visual recognition (ZSL), where test
images and their classes are both unseen during training. SP-AEN aims to tackle
the inherent problem --- semantic loss --- in the prevailing family of
embedding-based ZSL, where some semantics would be discarded during training if
they are non-discriminative for training classes, but could become critical for
recognizing test classes. Specifically, SP-AEN prevents the semantic loss by
introducing an independent visual-to-semantic space embedder which disentangles
the semantic space into two subspaces for the two arguably conflicting
objectives: classification and reconstruction. Through adversarial learning of
the two subspaces, SP-AEN can transfer the semantics from the reconstructive
subspace to the discriminative one, accomplishing the improved zero-shot
recognition of unseen classes. Comparing with prior works, SP-AEN can not only
improve classification but also generate photo-realistic images, demonstrating
the effectiveness of semantic preservation. On four popular benchmarks: CUB,
AWA, SUN and aPY, SP-AEN considerably outperforms other state-of-the-art
methods by an absolute performance difference of 12.2\%, 9.3\%, 4.0\%, and
3.6\% in terms of harmonic mean value
Unconventional Floquet topological phases from quantum engineering of band inversion surfaces
Floquet engineering provides a toolbox for the realization of novel quantum
phases without static counterparts, while conventionally the realization may
rely on the manipulation of complex temporal evolution. Here we propose a
systematic and high-precision scheme to realize unconventional Floquet
topological phases by engineering local band structures in particular momentum
subspace called band inversion surfaces (BISs). This scheme is based on a new
bulk-boundary correspondence that for a class of generic -dimensional
periodically driven systems, the local topological structure formed in each BIS
uniquely determines the features of gapless boundary modes. By engineering the
BIS configuration we demonstrate a highly efficient approach to realize,
manipulate, and detect novel Floquet topological phases. In particular, we
predict a two-dimensional (2D) anomalous Floquet valley-Hall phase which
carries trivial global bulk topological invariants but features protected
counter-propagating edge states in each quasienergy gap. The unconventional
nature of this novel 2D phase is further illustrated by the examination of edge
geometry dependence and its robustness to disorder scattering. Anomalous chiral
topological phases with valley protection in higher dimension are also
predicted and studied. Our systematic and highly feasible scheme opens a new
route to realize and engineer unconventional Floquet topological phases for
ultracold atoms and other quantum simulators.Comment: 16 pages, 7 figures. To appear in PRX Quantu
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