1,328 research outputs found
Dynamical tunneling-assisted coupling of high-Q deformed microcavities using a free-space beam
We investigate the efficient free-space excitation of high-Q resonance modes in deformed microcavities via dynamical tunneling-assisted coupling. A quantum scattering theory is employed to study the free-space transmission properties, and it is found that the transmission includes the contribution from (1) the off-resonance background and (2) the on-resonance modulation, corresponding to the absence and presence of high-Q modes, respectively. The theory predicts asymmetric Fano-like resonances around high-Q modes in background transmission spectra, which are in good agreement with our recent experimental results. Dynamical tunneling across Kolmogorov-Arnold-Moser tori, which plays an essential role in the Fano-like resonance, is further studied. This efficient free-space coupling holds potential advantages to simplify experimental conditions and excite high-Q modes in higher-index-material microcavities
Impact of Zr substitution on the electronic structure of ferroelectric hafnia
-based dielectrics are promising for nanoscale ferroelectric
applications, and the most favorable material within the family is
Zr-substituted hafnia, i.e., (HZO). The extent of Zr
substitution can be great, and x is commonly set to 0.5. However, the band gap
of is lower than , thus it is uncertain how
the Zr content should influence the electronic band structure of HZO. A reduced
band gap is detrimental to the cycling endurance as charge injection and
dielectric breakdown would become easier. Another issue is regarding the
comparison on the band gaps between /
superlattices and HZO solid-state solutions. In this work we systematically
investigated the electronic structures of ,
and HZO using self-energy corrected density functional theory. In particular,
the conduction band minimum of - is found to lie at an
ordinary k-point on the Brillouin zone border, not related to any interlines
between high-symmetry k-points. Moreover, the rule of HZO band gap variation
with respect to x has been extracted. The physical mechanisms for the
exponential reduction regime and linear decay regime have been revealed. The
band gaps of / ferroelectric superlattices are
investigated in a systematic manner, and the reason why the superlattice could
possess a band gap lower than that of is revealed through
comprehensive analysis.Comment: 23 pages, 9 figure
Surface Stabilization of O3-type Layered Oxide Cathode to Protect the Anode of Sodium Ion Batteries for Superior Lifespan
Even though the energy density of O3-type layer-structured metal oxide cathode can fully reach the requirement for large-scale energy storage systems, the cycling lifespan still cannot meet the demand for practical application once it is coupled with a non-sodium-metal anode in full-cell system. Transition metal dissolution into the electrolyte occurs along with continuous phase transformation and accelerates deterioration of the crystal structure, followed by migration and finally deposition on the anode to form a vicious circle. Surface engineering techniques are employed to modify the interface between active materials and the electrolyte by coating them with a thin layer of AlPO4 ion conductor. This stable thin layer can stabilize the surface crystal structure of the cathode material by avoiding element dissolution. Meanwhile, it can protect the anode from increased resistance by suppressing the dissolution-migration-deposition process. This technique is a promising method to improve the lifetime for the future commercialization
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