Hydrogen and hydrogen-like-ion bound states and hyperfine splittings: finite nuclear size effects}

Using the Dirac equation, we study corrections to electron binding energies and hyperfine splittings of atomic hydrogen and hydrogen-like ions due to finite nuclear size (FNS) effects, relativistic QED radiative corrections and nuclear recoil corrections. Three models for the charge distribution and the magnetic moment distribution within the nucleus are considered. Calculations are carried for light atoms (H, He and K) and heavy atoms (Rb, Cs, Pb, Bi, U). The FNS corrections to the ground-state energy are shown to be smaller than the electron-nucleus reduced mass corrections, and comparable to the relativistic QED radiative corrections for the light nuclei, but much larger than both these corrections for heavy nuclei. Comparison is made with an experiment on the $1s$-$2s$ transition frequency for hydrogen. FNS corrections to the ground state hyperfine splitting are comparable in size to the relativistic QED radiative corrections for light nuclei, but are larger for heavy nuclei.Comment: 33 pages, 13 figure

Kondo Tunneling into a Quantum Spin Hall Insulator

The physics of a junction composed of a normal metal, quantum dot and 2D topological insulator (in a quantum spin Hall state) is elucidated. It maifests a subtle combination of Kondo correlations and quantum spin Hall edge states moving on the opposite sides of the 2D topological insulator. In a narrow strip geometry these edge states interact and a gap opens in the edge state spectrum. Consequently, Kondo screening is less effective and that affects electron transport through the junction. Specifically, when edge state coupling is strong enough, the tunneling differential conductance develops a dip at zero temperature instead of the standard zero bias Kondo peak.Comment: 6 two-column pages, 4 .eps figure

Canted Magnetization Texture in Ferromagnetic Tunnel Junctions

We study the formation of inhomogeneous magnetization texture in the vicinity of a tunnel junction between two ferromagnetic wires nominally in the antiparallel configuration and its influence on the magnetoresistance of such a device. The texture, dependent on magnetization rigidity and crystalline anisotropy energy in the ferromagnet, appears upon an increase of ferromagnetic inter-wire coupling above a critical value and it varies with an external magnetic field.Comment: 5 pages, 4 figure

Atoms in a spin-dependent optical lattice potential as a topological insulator with broken time-reversal symmetry

We investigate fermionic $^{6}$Li $F= 1/2$ atoms in a 2D spin-dependent optical lattice potential (SDOLP) generated by intersecting laser beams with a superposition of polarizations. The effective interaction of a Li atom with the electromagnetic field contains a scalar and vector (called as fictitious magnetic field, ${\bf B}_\mathrm{fic}$) contribution. We calculate the band structure of Li atoms in the SDOLP as a function of the laser intensity and an external magnetic field ${\bf B}_{\mathrm{ext}} = B_{\mathrm{ext}} {\hat {\bf z}}$. We also calculate the Chern numbers of the SDOLP and show that depending on $B_{\mathrm{ext}}$, the system is an ordinary insulator, an Abeliean topological insulator (TI), or a non-Abelian TI. Introducing a blue-detuned laser potential, $V_{\mathrm{BD}}(y) = V_{\mathrm{BD},0}(y) \Theta (|y| - L_y/2)$, results in edges for the SDOL. We calculate the resulting edge states (some of which are topological) and study their density, current density, spin-current density and correlate the edge states with the Chern numbers.Comment: 5 pages, 4 eps figures and Supplementary material