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Classical rotations of asymmetric rigid bodies are unstable around the axis of intermediate momentof inertia, causing a flipping of rotor orientation. This effect, known as the tennis racket effect,quickly averages to zero in classical ensembles since the flipping period varies significantly uponapproaching the separatrix. Here, we explore the quantum rotations of rapidly spinning thermalasymmetric nanorotors and show that classically forbidden tunnelling gives rise to persistent tennisracket dynamics, in stark contrast to the classical expectation. We characterise this effect, demon-strating that quantum coherent flipping dynamics can persist even in the regime where millions ofangular momentum states are occupied. This persistent flipping offers a promising route for observ-ing and exploiting quantum effects in rotational degrees of freedom for molecules and nanoparticles., Comment: 12 pages, 8 figures

The integer quantum Hall effect (IQHE) and chaos are commonly conceived as being unrelated. Contrary to common wisdoms, we find in a canonical chaotic system, the kicked spin-$1/2$ rotor, a Planck's quantum($h_e$)-driven phenomenon bearing a firm analogy to IQHE but of chaos origin. Specifically, the rotor's energy growth is unbounded ('metallic' phase) for a discrete set of critical $h_e$-values, but otherwise bounded ('insulating' phase). The latter phase is topological in nature and characterized by a quantum number ('quantized Hall conductance'). The number jumps by unity whenever $h_e$ decreases passing through each critical value. Our findings, within the reach of cold-atom experiments, indicate that rich topological quantum phenomena may emerge from chaos., Comment: Fig. 1 and 2 modified

Three sets of chiral doublet band structures have been identified in the $^{103}\mathrm{Rh}$ nucleus. The properties of the observed chiral doublet bands are in good agreement with theoretical results obtained using constrained covariant density functional theory and particle rotor model calculations. Two of them belong to an identical configuration and provide the first experimental evidence for a novel type of multiple chiral doublets, where an ``excited'' chiral doublet of a configuration is seen together with the ``yrast'' one. This observation shows that the chiral geometry in nuclei can be robust against the increase of the intrinsic excitation energy.

The anharmonic vibrator and rotor regions in nuclei are investigated in the framework of the interacting boson model using an ensemble of random one- and two-body interactions. We find a predominance of L(P)=0(+) ground states, as well as strong evidence for the occurrence of both vibrational and rotational band structures. This remarkable result suggests that such band structures represent a far more general (robust) property of the collective model space than is generally thought., Comment: 5 pages, 4 figures, Phys. Rev. Lett., in press

We construct a simple semiclassical argument to correlate dynamical localization, observed in several nonintegrable quantum dynamics, with the dominance of diffusive periodic orbits over ballistic ones. We use the kicked rotor (and modifications thereof) dynamics to illustrate the procedure though the argument is valid for any quantum dynamical system fulfilling certain nondegeneracy conditions and which shows deterministic diffusion in the classical limit.

We demonstrate that the quantum localization (narrowed momentum distributions) observed in the recent momentum transfer experiments may be associated with the influence of classical phase space resonance structures on quantum Floquet states. By numerically investigating the evolution of initial distributions located in chaotic regions of the classical phase space, we argue that dynamical localization, seen, for example, in quantum kicked rotor models, is not the only possible explanation of the observed localized momentum distributions. {copyright} {ital 1995} {ital The} {ital American} {ital Physical} {ital Society}.

A two-dimensional generalization of the one-dimensional kicked-rotor model is introduced. As in one dimension, this model can be mapped on a two-dimensional Anderson model for localization. It is found that all the states are localized in momentum space and that the localization length grows exponentially with the mean free path, as expected from the scaling theory for localization. This suggests that the correspondence between the quantum dynamics of chaotic systems and Anderson localization that was found in one dimension holds in two dimensions as well.

Each weight change of three spinning mechanical gyroscopes whose rotor's masses are 140, 175, and 176 g has been measured in inertial rotations without systematic errors. The experiments show that the weight changes on rotations around the vertical axis are completely asymmetrical: The right rotations (spin vector pointing downwards) cause weight decrease of the order of milligrams (weight), proportional to the frequency of rotations at 3 000--13 000 rpm. However, the left rotations do not cause any change in weight.