762 research outputs found
Electrical characterization of graphene source/drain electrodes in amorphous indium-gallium-zinc-oxide thin-film transistors subjected to plasma treatment in contact regions
No full textIn this paper, the electrical characteristics of a-IGZO TFTs with graphene source/drain (S/D) electrodes subjected to argon plasma treatment are analyzed. Depending on the channel length (L), the a-IGZO TFTs showed parasitic resistance dominant (L < 30 μm) and channel conduction dominant regions (L ≥ 30 μm). Using the transmission line method, the intrinsic parameters were extracted. The intrinsic field-effect mobility was about 9.79 cm2 V-1 s-1 and the width-normalized parasitic resistance value was about 460 Ωcm, which are comparable with those of a-IGZO TFTs having S/D plasma-treated regions with no contact metal. Temperature-dependent measurement indicates that the graphene electrodes affected the thermally deactivated behavior of the a-IGZO TFTs, which is different from the case of a-IGZO TFTs having conventional metal electrodes. © 2019 The Japan Society of Applied Physics.1
Spectro-spatial coherent control of ultrafast laser interaction with atomic vapor
No full textSpectro-spatial coherent control methods are reported demonstrating optimized resonant two-photon transitions of rubidium atomic vapor by counter-propagating ultrashort pulse pairs. By properly programming the spectral sign changes across resonance frequencies, unlike non-resonant two-photon transitions, the resonant two-photon transitions probabilities could be enhanced, experiment finds
Lagrange-sinc basis set for efficient electronic structure calculations
No full textAbstract:Density functional theory (DFT) is certainly the most popular method for electronic structure calculations, because it provides a cost-effective means of obtaining reliable results for various applications. Though DFT is formally exact, its numerical accuracy and efficiency is sensitive to the type of basis sets, since it determines the completeness of variational space and the numerical algorithm for solving Schrödinger equation, respectively. Recently, we developed a self-consistent field program based on DFT using Lagrange-sinc functions (LSFs) as a basis set. Though the Lagrange-sinc basis set is based numerical grids, it offers analytical evaluation for Laplacian and some local potential integrals, allowing for rapid and accurate calculations of Hartree terms and pseudopotential integrals. In addition, scalable-parallelization is possible up to thousands cores. Use of multi-grids effectively removes the so-called egg-box effect and greatly reduces computational costs thanks to large grid spacing. We have also extended our code to multiconfiguration methods with a reference configuration obtained from exact exchange Kohn-Sham orbitals, which allows more efficient calculations compared to standard post-Hartree-Fock approaches. In this talk, we present details of our method and numerical results for ground and excited state calculations.
[1] Sunghwan Choi, Kwangwoo Hong, Jaewook Kim, and Woo Youn Kim, Accuracy of Lagrange-sinc Functions as a Basis Set for Electronic Structure Calculations of Atoms and Molecules, J. Chem. Phys. 2015, 142, 094116.
[2] Jaewook Kim, Kwangwoo Hong, Sunghwan Choi, and Woo Youn Kim, Feature of Exact Exchange Kohn-Sham Orbitals with Krieger-Li-Iafrate Approximation, Bull. Korean Chem. Soc. 2015, 36, 998-1007.
[3] Jaewook Kim, Kwangwoo Hong, Sunghwan Choi, Sang-Yeon Hwang, and Woo Youn Kim, Configuration Interaction Singles based on Real-Space Numerical Grid Method: Kohn-Sham versus Hartree-Fock Orbitals, Phys. Chem. Chem. 2015, Phys. in revision
Atomic Quantum Wires in Ising-spin Chain Models
No full textWe implement quantum wires in Rydberg atom systems to program graph-connected Ising spins. With auxiliary atoms arranged in wires, we show that non-adjacent qubits are on-demand coupled for an Ising Hamiltonian of arbitrary graph connections
Generating synthetic 3D density fluctuation data to verify two-point measurement of parallel correlation length
No full textQuantum Ising Hamiltonian Programming in Trio, Quartet, and Sextet Qubit Systems
No full textRydberg-atom quantum simulators are of keen interest because of their possibilities towards high-dimensional qubit architectures. Here we report continuous tuning of quantum Ising Hamiltonians of Rydberg atoms in three-dimensional arrangements. Various connected graphs of Rydberg atoms constructed with vertices and edges respectively representing atoms and Rydberg-blockaded atom pairs, and their eigenenergies are probed along with their geometric intermediates during structural transformations. Conformation spectra of star, complete, cyclic, and diamond graphs are probed for four interacting atoms and antiprism structures for six atoms. The energy level shifts and merges of the tested structural transformations are clearly observed with Fourier-transform spectroscopy, in good agreement with the model few-body quantum Ising Hamiltonian. This result demonstrates the possibility of continuous geometry tuning and thus programming of many-body spin-Hamiltonian systems.
Quantum simulation with N=19 Rydberg atoms for quantum Ising dynamics
No full textN = 19 rubidium atoms are loaded with holographic optical tweezers in a zig-zag chain and entangled through collective Rabi oscillation to Rydberg state. Resulting coherent dynamics manifests quantum simulation of 1D quantum-Ising model with controlled frustrations
전산공력음향학을 위한 적응형 비선형 인공감쇄모형
No full textAn adaptive nonlinear artificial dissipation model is presented for performing aeroacoustic computations by the high-order and high-resolution numerical schemes based on the central finite differences. An effective formalism of it is devised by combining a selective background smoothing term and a well-established nonlinear shock-capturing term which is for the temporal accuracy as well as the numerical stability. A conservative form of the selective background smoothing term is presented to keep accurate phase speeds of the propagating nonlinear waves. The nonlinear shock-capturing term that has been modeled by the second-order derivative term is combined with it to improve the resolution of discontinuities and stabilize the strong nonlinear waves. It is shown that the improved artificial dissipation model with an adaptive control constant which is independent of problem types reproduces the correct profiles and speeds of nonlinear waves, suppresses numerical oscillations near discontinuity and avoids unnecessary damping on the smooth linear acoustic waves. The feasibility and performance of the adaptive nonlinear artificial dissipation model are investigated by the applications to actual computational aeroacoustics problems
Triboelectrification charge modulation with modified high dielectric nanoparticles for improvement performance of triboelectric nanogenerators
No full text3D Bioprinting of Islet-like Aggregates Using Dual-crosslinked Hydrogel with Promoted Biofunctionality and Enhanced Shape Stability
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