30 research outputs found
Quantum Sensing of Single Phonons via Phonon Drag in Two-Dimensional Materials
The capacity to electrically detect phonons, ultimately at the single-phonon
limit, is a key requirement for many schemes for phonon-based quantum
computing, so-called quantum phononics. Here, we predict that by exploiting the
strong coupling of their electrons to surface-polar phonons, van der Waals
heterostructures can offer a suitable platform for phonon sensing, capable of
resolving energy transfer at the single-phonon level. The geometry we consider
is one in which a drag momentum is exerted on electrons in a graphene layer, by
a single out-of-equilibrium phonon in a dielectric layer of hexagonal boron
nitride, giving rise to a measurable induced voltage (). Our
numerical solution of the Boltzmann Transport Equation shows that this drag
voltage can reach a level of a few hundred microvolts per phonon, well above
experimental detection limits. Furthermore, we predict that
should be highly insensitive to the mobility of carriers in the graphene layer
and to increasing the temperature to at least 300 K, offering the potential of
a versatile material platform for single-phonon sensing.Comment: 13 pages, 6 figure
Coupled Eulerian-Lagrangian Debris Flow Model with Flexible Barrier
Natural hazards such as large debris flow events can have catastrophic effects on the environment and critical infrastructure, posing a significant threat to human life. Debris flows often exhibit high velocity, high-pressure discharges due to their bulk volume, and the capacity to transport considerable volumes of large rocks, boulders, and woody debris. Although debris flow run-out simulations are commonly performed using hydraulic modelling software, these environments are seldom capable of assessing the interaction between the debris fluid, transported material, and protective structures. In this research, large deformation numerical models are calibrated using input parameters from hydraulic modelling software. Due to the computational cost of the large deformation models involving fluid-solid-structure simulation with flexible net barriers, an equivalent stiffness method is implemented to provide comparable performance through a membrane structure. The Coupled Eulerian-Lagrangian Finite Element method is used to model the impact forces of rocky boulders on the membrane, exhibiting damage characteristics consistent with flexible ring-net protective structures. The Coupled Eulerian-Lagrangian model results highlight the performance of the simplified membrane, as shown through a benchmark simulation of debris flow with boulders
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Dielectric Engineering Boosts the Efficiency of Carbon Nanotube Photodiodes
Carbon nanotube (CNT) photodiodes are a promising system for high-efficiency photocurrent generation due to the strong Coulomb interactions that can drive carrier multiplication. If the Coulomb interactions are too strong, however, exciton formation can hamper photocurrent generation. Here, we explore, experimentally and theoretically, the effect of the environmental dielectric constant (ε_env) on the photocurrent generation process in CNTs. We study individual ultra-clean CNTs of known chiral index in vacuum or dry nitrogen gas (ε_env = 1) and oil (ε_env = 2.15). The efficiency of photocurrent generation improves by more than an order of magnitude in oil. Two mechanisms explain this improvement. First, the refractive index of the environment optimizes the interference between incident and reflected light. Second, exciton binding energies are reduced in oil, changing the relaxation pathways of photoexcited carriers. We varied the axial electric field in the pn junction from 4 to 14 V/μm. Our measurements at high field indicate that autoionization of second-subband excitons can coexist with carrier multiplication. Dielectric screening makes this coexistence regime more accessible and allows us to reach photocurrent quantum yields greater than 100%
G-Jitter impact on magnetohydrodynamic non-Newtonian fluid over an inclined surface: Finite element simulation
Analysis of natural convection and entropy generation in a cavity filled with multi-layers of porous medium and nanofluid with a heat generation
Tuning the Electronic Properties of Symetrical and Asymetrical Boron Nitride Passivated Graphene Nanoribbons: Density Function Theory
Coupled Eulerian-Lagrangian Debris Flow Model with Flexible Barrier
Natural hazards such as large debris flow events can have catastrophic effects on the environment and critical infrastructure, posing a significant threat to human life. Debris flows often exhibit high velocity, high-pressure discharges due to their bulk volume, and the capacity to transport considerable volumes of large rocks, boulders, and woody debris. Although debris flow run-out simulations are commonly performed using hydraulic modelling software, these environments are seldom capable of assessing the interaction between the debris fluid, transported material, and protective structures. In this research, large deformation numerical models are calibrated using input parameters from hydraulic modelling software. Due to the computational cost of the large deformation models involving fluid-solid-structure simulation with flexible net barriers, an equivalent stiffness method is implemented to provide comparable performance through a membrane structure. The Coupled Eulerian-Lagrangian Finite Element method is used to model the impact forces of rocky boulders on the membrane, exhibiting damage characteristics consistent with flexible ring-net protective structures. The Coupled Eulerian-Lagrangian model results highlight the performance of the simplified membrane, as shown through a benchmark simulation of debris flow with boulders
MHD effect on mixed convection of annulus circular enclosure filled with Non-Newtonian nanofluid
Tunable interlayer excitons and switchable interlayer trions via dynamic near-field cavity
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