Two-electron photoionization of endohedral atoms

Using $He@C_{60}$ as an example, we demonstrate that static potential of the fullerene core essentially alters the cross section of the two-electron ionization differential in one-electron energy $d\sigma ^{++}(\omega )/d\epsilon$. We found that at high photon energy prominent oscillations appear in it due to reflection of the second, slow electron wave on the $C_{60}$ shell, which "dies out" at relatively high $\epsilon$ values, of about 2$\div$3 two-electron ionization potentials. The results were presented for ratios $R_{C_{60}}(\omega ,\epsilon)\equiv d\sigma ^{++}(\omega ,\epsilon)/d\sigma ^{a++}(\omega,\epsilon)$, where $d\sigma ^{a++}(\omega,\epsilon)/d\epsilon$ is the two-electron differential photoionization cross section. We have calculated the ratio $R_{i,ful}= \sigma_{i} ^{++}(\omega)/\sigma_{i}^{a++}(\omega)$, that accounts for reflection of both photoelectrons by the $C_{60}$ shell. We have calculated also the value of two-electron photoionization cross section $\sigma ^{++}(\omega)$ and found that this value is close to that of an isolated $He$ atom.Comment: 13 pages, 4 figure

A possible supersymmetric solution to the discrepancy between B -> \phi K_S and B -> \eta' K_S CP asymmetries

We present a possible supersymmetric solution to the discrepancy between the observed mixing CP asymmetries in B -> \phi K_S and B -> \eta' K_S. We show that due to the different parity in the final states of these processes, their supersymmetric contributions from the R-sector have an opposite sign, which naturally explain the large deviation between S_{\phi K_S} and S_{\eta' K_S}. We also consider the proposed mechanisms to solve the puzzle of the observed large branching ratio of B -> \eta' K and study their impact on S_{eta' K_S}.Comment: 4 pages, 2 figure

Anomalous Spin Dynamics of Hubbard Model on Honeycomb Lattices

In this paper, the honeycomb Hubbard model in optical lattices is investigated using O(3) non-linear sigma model. A possible quantum non-magnetic insulator in a narrow parameter region is found near the metal-insulator transition. We study the corresponding dynamics of magnetic properties, and find that the narrow region could be widened by hole doping.Comment: 9 pages, 12 figure

Sub-wavelength focusing of high intensities in microfibre tips

Sub-wavelength efficient intensity confinement has been demonstrated in nanostructured optical microfibre tips. Focus Ion Beam (FIB) milling was used to nanostructure gold-coated optical microfibre tips and form apertures at the apex. Simulations were carried out to optimize the device design. Enhanced transmission efficiency (higher than 10-2) was achieved in spot sizes of ~λ/10. Nanostructured microfibre tips have the potential for a number of applications including optical recording, photolithography and scanning near-field optical microscopy (SNOM)

Resonant magneto-optic Kerr effect in the magnetic topological insulator Cr:(Sbx_x,Bi1−x_{1-x})2_2Te3_3

We report measurements of the polar Kerr effect, proportional to the out-of-plane component of the magnetization, in thin films of the magnetically doped topological insulator $(\text{Cr}_{0.12}\text{Bi}_{0.26}\text{Sb}_{0.62})_2\text{Te}_3$. Measurements of the complex Kerr angle, $\Theta_K$, were performed as a function of photon energy in the range $0.8\text{ eV}<\hbar\omega<3.0\text{ eV}$. We observed a peak in the real part of $\Theta_K(\omega)$ and zero crossing in the imaginary part that we attribute to resonant interaction with a spin-orbit avoided crossing located $\approx$ 1.6 eV above the Fermi energy. The resonant enhancement allows measurement of the temperature and magnetic field dependence of $\Theta_K$ in the ultrathin film limit, $d\geq2$ quintuple layers. We find a sharp transition to zero remanent magnetization at 6 K for $d<8$~QL, consistent with theories of the dependence of impurity spin interactions on film thickness and their location relative to topological insulator surfaces.Comment: 6 pages, 5 figure