The effect of an ac electric field on quantum transport properties in a system of three quantum dots, two of which are connected in parallel while the third is coupled to one of the other two, is investigated theoretically. Based on the Keldysh nonequilibrium Green's function method, the spin-dependent current, occupation number and spin accumulation can be obtained in our model. An external magnetic flux, Rashba spin orbit coupling (SOC) and intradot Coulomb interactions are considered. The magnitude of the spin-dependent average current and the positions of the photon assisted tunneling (PAT) peaks can be accurately controlled and manipulated by simply varying the strength of the coupling and the frequency of the ac field. A particularly interesting result is the observation of a new kind of PAT peak and a multiple electron-photon pump effect that can generated and controlled by the coupling between the quantum dots. In addition, the spin occupation number and spin accumulation can be well controlled by the Rashba SOC and the magnetic flux.

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We report the correlation between atomic size ratio and Poisson's ratio in various metallic glasses. It is found that atomic size ratio has an influence on the atomic packing density of metallic glasses, which would significantly impact the shear modulus rather than bulk modulus. The findings may be helpful for understanding the structural origin of Poisson's ratio in metallic glasses, and are instructive for designing tough metallic glasses with large Poisson's ratio.

The relationship between the slowness curved surface and the softening of the acoustic mode is discussed. The acoustic mode softening of hexagonal system corresponds to the maximum slowness. The eigenvector of soft mode corresponds to the polarization of acoustic mode. By solving the Christoffel equation, the maximum slowness and the polarization of the acoustic mode can be obtained. The symmetry change of proper ferroelastic phase transition can be determined by analyzing the solutions of the Christoffel equation and by using Curie principle.

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