Nonequilibrium nuclear-electron spin dynamics in semiconductor quantum dots

We study the spin dynamics in charged quantum dots in the situation where the resident electron is coupled to only about 200 nuclear spins and where the electron spin splitting induced by the Overhauser field does not exceed markedly the spectral broadening. The formation of a dynamical nuclear polarization as well as its subsequent decay by the dipole-dipole interaction is directly resolved in time. Because not limited by intrinsic nonlinearities, almost complete nuclear polarization is achieved, even at elevated temperatures. The data suggest a nonequilibrium mode of nuclear polarization, distinctly different from the spin temperature concept exploited on bulk semiconductorsComment: 5 pages, 4 figure

Magneto-Optical Trap for Thulium Atoms

Thulium atoms are trapped in a magneto-optical trap using a strong transition at 410 nm with a small branching ratio. We trap up to $7\times10^{4}$ atoms at a temperature of 0.8(2) mK after deceleration in a 40 cm long Zeeman slower. Optical leaks from the cooling cycle influence the lifetime of atoms in the MOT which varies between 0.3 -1.5 s in our experiments. The lower limit for the leaking rate from the upper cooling level is measured to be 22(6) s$^{-1}$. The repumping laser transferring the atomic population out of the F=3 hyperfine ground-state sublevel gives a 30% increase for the lifetime and the number of atoms in the trap.Comment: 4 pages, 6 figure

Observation of non-local dielectric relaxation in glycerol

Since its introduction, liquid viscosity and relaxation time $\tau$ have been considered to be an intrinsic property of the system that is essentially local in nature and therefore independent of system size. We perform dielectric relaxation experiments in glycerol, and find that this is the case at high temperature only. At low temperature, $\tau$ increases with system size and becomes non-local. We discuss the origin of this effect in a picture based on liquid elasticity length, the length over which local relaxation events in a liquid interact via induced elastic waves, and find good agreement between experiment and theory