3,544 research outputs found
Bipolaronic blockade effect in quantum dots with negative charging energy
We investigate single-electron transport through quantum dots with negative
charging energy induced by a polaronic energy shift. For weak dot-lead tunnel
couplings, we demonstrate a bipolaronic blockade effect at low biases which
suppresses the oscillating linear conductance, while the conductance resonances
under large biases are enhanced. Novel conductance plateau develops when the
coupling asymmetry is introduced, with its height and width tuned by the
coupling strength and external magnetic field. It is further shown that the
amplitude ratio of magnetic-split conductance peaks changes from 3 to 1for
increasing coupling asymmetry. Though we demonstrate all these transport
phenomena in the low-order single-electron tunneling regime, they are already
strikingly different from the usual Coulomb blockade physics and are easy to
observe experimentally.Comment: 6 pages, 5 figure
Coordinated Operation of the Electricity and Natural Gas Systems with Bi-directional Energy Conversion
Diverse anisotropy of phonon transport in two-dimensional IV-VI compounds: A comparative study
New classes two-dimensional (2D) materials beyond graphene, including layered
and non-layered, and their heterostructures, are currently attracting
increasing interest due to their promising applications in nanoelectronics,
optoelectronics and clean energy, where thermal transport property is one of
the fundamental physical parameters. In this paper, we systematically
investigated the phonon transport properties of 2D orthorhombic group IV-VI
compounds of , , and by solving the Boltzmann transport
equation (BTE) based on first-principles calculations. Despite the similar
puckered (hinge-like) structure along the armchair direction as phosphorene,
the four monolayer compounds possess diverse anisotropic properties in many
aspects, such as phonon group velocity, Young's modulus and lattice thermal
conductivity (), etc. Especially, the along the zigzag and
armchair directions of monolayer shows the strongest anisotropy while
monolayer and shows an almost isotropy in phonon transport. The
origin of the diverse anisotropy is fully studied and the underlying mechanism
is discussed in detail. With limited size, the could be effectively
lowered, and the anisotropy could be effectively modulated by nanostructuring,
which would extend the applications in nanoscale thermoelectrics and thermal
management. Our study offers fundamental understanding of the anisotropic
phonon transport properties of 2D materials, and would be of significance for
further study, modulation and aplications in emerging technologies.Comment: 14 pages, 8 figures, 2 table
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High reward enhances perceptual learning.
Studies of perceptual learning have revealed a great deal of plasticity in adult humans. In this study, we systematically investigated the effects and mechanisms of several forms (trial-by-trial, block, and session rewards) and levels (no, low, high, subliminal) of monetary reward on the rate, magnitude, and generalizability of perceptual learning. We found that high monetary reward can greatly promote the rate and boost the magnitude of learning and enhance performance in untrained spatial frequencies and eye without changing interocular, interlocation, and interdirection transfer indices. High reward per se made unique contributions to the enhanced learning through improved internal noise reduction. Furthermore, the effects of high reward on perceptual learning occurred in a range of perceptual tasks. The results may have major implications for the understanding of the nature of the learning rule in perceptual learning and for the use of reward to enhance perceptual learning in practical applications
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