Dynamics of magnetization in frustrated spin-chain systems: Ca3_3Co2_2O6_6

The magnetization dynamics of the triangular lattice of Ising spin chains is investigated in the framework of a two-dimensional model. The rigid chains are assumed to interact with the nearest neighboring chains, an external magnetic field, and a heat reservoir that causes the chains to change their states randomly with time. A probability of a single spin-flip process is assumed in a Glauber-like form. This technique allows describing properly the steps in the magnetization curves observed in Ca$_3$Co$_2$O$_6$ and their dependence on a magnetic field sweep rate and temperature. A transition from a low-temperature to high-temperature phase is also observed.Comment: 3.5 pages, 3 figures, submitted to PR

Temperature-dependent magnetospectroscopy of HgTe quantum wells

We report on magnetospectroscopy of HgTe quantum wells in magnetic fields up to 45 T in temperature range from 4.2 K up to 185 K. We observe intra- and inter-band transitions from zero-mode Landau levels, which split from the bottom conduction and upper valence subbands, and merge under the applied magnetic field. To describe experimental results, realistic temperature-dependent calculations of Landau levels have been performed. We show that although our samples are topological insulators at low temperatures only, the signature of such phase persists in optical transitions at high temperatures and high magnetic fields. Our results demonstrate that temperature-dependent magnetospectroscopy is a powerful tool to discriminate trivial and topological insulator phases in HgTe quantum wells

High-harmonic generation from a confined atom

The order of high harmonics emitted by an atom in an intense laser field is limited by the so-called cutoff frequency. Solving the time-dependent Schr\"odinger equation, we show that this frequency can be increased considerably by a parabolic confining potential, if the confinement parameters are suitably chosen. Furthermore, due to confinement, the radiation intensity remains high throughout the extended emission range. All features observed can be explained with classical arguments.Comment: 4 pages(tex files), 4 figures(eps files); added references and comment