5,168 research outputs found
Topological Imbert-Fedorov shift in Weyl semimetals
The Goos-H\"anchen (GH) shift and the Imbert-Fedorov (IF) shift are optical
phenomena which describe the longitudinal and transverse lateral shifts at the
reflection interface, respectively. Here, we report the GH and IF shifts in
Weyl semimetals (WSMs) - a promising material harboring low energy Weyl
fermions, a massless fermionic cousin of photons. Our results show that GH
shift in WSMs is valley-independent which is analogous to that discovered in a
2D relativistic material - graphene. However, the IF shift has never been
explored in non-optical systems, and here we show that it is valley-dependent.
Furthermore, we find that the IF shift actually originates from the topological
effect of the system. Experimentally, the topological IF shift can be utilized
to characterize the Weyl semimetals, design valleytronic devices of high
efficiency, and measure the Berry curvature
Coherent Single Spin Source based on topological insulator
We report on the injection of quantized pure spin current into quantum
conductors. In particular, we propose an on demand single spin source generated
by periodically varying the gate voltages of two quantum dots that are
connected to a two dimensional topological insulator via tunneling barriers.
Due to the nature of the helical states of the topological insulator, one or
several {\it spin pair}s can be pumped out per cycle giving rise to a pure
quantized alternating spin current. Depending on the phase difference between
two gate voltages, this device can serve as an on demand single spin emitter or
single charge emitter. Again due to the helicity of the topological insulator,
the single spin emitter or charge emitter is dissipationless and immune to
disorders. The proposed single spin emitter can be an important building block
of future spintronic devices.Comment: 5 pages, 4 figures, append one co-author that has been misse
Numerical investigation on aggregate settlement and its effect on the durability of hardened concrete
Vibrating consolidation process is widely applied to field construction of cement concrete. However, high-frequency vibration can easily lead to the settlement of coarse aggregates (CAs) and then affects the durability of hardened concrete. This study has developed a 3-D concrete model to investigate the CA settlement caused by vibration and its effect on long-term chloride transport in concrete. Based on the proposed model, the influence mechanism of CA settlement on both chloride concentration distribution and initiation time of reinforcement corrosion is discussed in detail. The results indicate that due to the settlement, a more obvious fluctuation of chloride concentration along the height direction of concrete specimen can be observed with the increase of vibration time. According to the model prediction, the corrosion of the top steel bar initiates 1.03–1.80 years earlier than that of the bottom steel bar under different vibration time. The proposed model provides a new method to probe into the influence of vibration-induced settlement on chloride ingress in hardened concrete
The topological system with a twisting edge band: position-dependent Hall resistance
We study a topological system with one twisting edge-state band and
one normal edge-state band. For the twisting edge-state band, Fermi energy goes
through the band three times, thus, having three edge states on one side of the
sample; while the normal edge band contributes only one edge state on the other
side of the sample. In such a system, we show that it consists of both
topologically protected and unprotected edge states, and as a consequence, its
Hall resistance depends on the location where the Hall measurement is done even
for a translationally invariant system. This unique property is absent in a
normal topological insulator
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