A Measure of Non-Classicality of Even and Odd Coherent States

A measure of non-classicality of even and odd coherent states is studied. We first calculate the Wigner functions of the even and odd coherent states, which consists of two terms： the positive-definite Gaussian term and the wave term with negativity, and then calculate the integrated value εmax of the wave term of the Wigner functions of the even and odd coherent states in their area with negativity, and use εmax to measure non-classicality of the even and odd coherent states. For the even and odd coherent states with certain photon count, it is very convenient for us to use εmax to measure their non-classicality. The methods of our definition and calculation for εmax have theoretical reference value.

Mechanical Properties and Electronic Structure of N and Ta Doped TiC: A First-Principles Study

The first principles calculations based on density functional theory(DFT) are employed to investigate the mechanical properties and electronic structure of N and Ta doped Ti C. The result shows that the co-doping of nitrogen and tantalum dilates the lattice constant and improves the stability of Ti C. Nitrogen and tantalum can significantly enhance the elastic constants and elastic moduli of Ti C. The results of B/G and C12-C44 indicate tantalum can markedly increase the ductility of Ti C. The electronic structure is calculated to describe the bonding characteristic, which revealed the strong hybridization between C-p and Ta-d and between N-p and Ti-d. The hardnessis is estimated by a semiempirical model that is based on the Mulliken overlap population and bond length. While the weakest bond takes determinative role of the hardness of materials, the addition of Ta sharply reduces the hardness of Ti C.

Distinguishing high-harmonic generation from surface and bulk states in topological insulator Bi_(2)Se_(3)

We demonstrated a scheme to differentiate the high-harmonic generation[HHG)originating from the surface states and bulk states of the topological insulator Bi_(2)Se_(3).By adopting two-color mid-infrared laser fields on Bi_(2)Se_(3),we found that the nonlinear response sensitively depends on the relative phase of the driving fields.The even harmonics arise from the surface states with a clear signature,whose modulation period equals the cycle of the second-harmonic generation[SHG]field.We reveal that the weak SHG perturbs the nontrivial dipole phase of the electron-hole pair in surface states,and thus leads to the modulation of HHG.It provides a means to manipulate the ultrafast dynamics in surface states through adopting a weak perturbing laser field.

The optical–electrical properties of doped β-FeSi_2

By using the pseudo-potential plane-wave method of first principles based on the density function theory, the geometrical, electronic structures and optical properties of FeSil.875M0.125 （M = B, N, A1, P） were calculated and analyzed. The calculated structural parameters depend strongly on the kinds of dopants and sites. The total energy calculations for substitution of dopants at the SiI and the SiII sites revealed that A1 and P prefer the SiI sites, whereas B and N prefer the SilI sites. The calculations predict that B- and Al-doped β-FeSi2 show p-type conduction, while N- and P-doped show n-type. Optical property calculations show that N-doping has little influence on the complex dielectric function of β-FeSi2; B-, N-, A1- and P-doping can enhance the electronic transition, refractive index, and reflection effect in the low-energy range, and weaken the reflection effect at the max peak of reflectivity. These results can offer theoretical guidance for the design and application of optoelectronic material β-FeSi2.