Table of contents

We study the quantum probability to survive in an open chaotic system in the framework of the van Vleck-Gutzwiller propagator and present the first such calculation that accounts for quantum interference effects. Specifically, we calculate quantum deviations from the classical decay after the break time t* for both broken and preserved time-reversal symmetry. The source of these corrections is identified in interfering pairs of correlated classical trajectories. In our approach the quantized chaotic system is modelled by a quantum graph.

The interplay between self-diffusion and excitation lines in space-time was recently studied in kinetically constrained models to explain the breakdown of the Stokes-Einstein law in supercooled liquids. Here, we further examine this interplay and its manifestation in incoherent scattering functions. In particular, we establish a dynamic length scale below which Fickian diffusion breaks down, as is observed in experiments and simulations. We describe the temperature dependence of this length scale in liquids of various fragilities, and provide analytical estimates for the van Hove and self-intermediate scattering functions.

We study the mechanisms responsible for quantum diffusion in the quasiperiodic kicked rotor. We report experimental measurements of the diffusion constant on the atomic version of the system and develop a theoretical approach (based on the Floquet theorem) explaining the observations, especially the "sub-Fourier" character of the resonances observed in the vicinity of exact periodicity, i.e. the ability of the system to distinguish two neighboring driving frequencies in a time shorter than the inverse of the difference of the two frequencies.

Heterogeneity in the degree (connectivity) distribution has been shown to suppress synchronization in networks of symmetrically coupled oscillators with uniform coupling strength (unweighted coupling). Here we uncover a condition for enhanced synchronization in weighted networks with asymmetric coupling. We show that, in the optimum regime, synchronizability is solely determined by the average degree and does not depend on the system size and the details of the degree distribution. In scale-free networks, where the average degree may increase with heterogeneity, synchronizability is drastically enhanced and may become positively correlated with heterogeneity, while the overall cost involved in the network coupling is significantly reduced as compared to the case of unweighted coupling.

It is shown that a pointlike composite having charge and magnetic moment displays a confining potential for the static interaction while simultaneously obeying fractional statistics in a pure gauge theory in three dimensions, without a Chern-Simons term. This result is distinct from the Maxwell-Chern-Simons theory that shows a screening nature for the potential.

We introduce new realistic brane solutions with exponential scale factors in the 6D space-time. We show that for these solutions the zero modes of all bulk fields are sharply localized at different positions on the brane and have "Gaussian shape" wave functions in the extra space. We also explicitly show that in the model there are cases when exactly three fermion generations naturally arise only through gravity. Because localized fermion modes are also stuck at different positions in the extra space, there is the possibility to provide a framework for naturally explaining the fermion mass hierarchy in terms of higher-dimensional geography.

We study K+Ar collisions by laser excitation of the collision pair in a differential scattering experiment. The relative population of the K(4p)²P fine-structure sublevels reflects the nonadiabatic coupling in the convergence region of the interaction potentials and illustrates the energy dependence of the nonadiabatic transition probability. Close coupling scattering calculations show a very good agreement with the experimental results, indicating a corresponding accuracy of the available potential data. The spin-orbit interaction in the coupling region is found to be not significantly different from the free atom value.

Heat conduction in a one-dimensional Yukawa chain is investigated. It is shown that the heat conductivity is abnormal in the absence of external potential. Effects of symmetric and asymmetric external potentials on the heat conduction of the system are also studied. It is found that the heat fluxes along opposite directions can be significantly different. One can control the heat flux through the external potential, which can induce a conductor-insulator transition of the system.

By examining the initial stages of the impact of a granular jet on a flat horizontal solid surface we evidenced the existence of oscillatory sand fronts. These oscillations give rise to a novel mechanism for the formation of ripples on sand surfaces. We here show that as the front advances, its slope changes periodically in time, leaving behind a succession of surface elevations and depressions. A key feature of these oscillations is the interplay between the deposition of mobile sand and the avalanching of the static parts giving rise to a remarkable self-regulating system. These features come out naturally from a simplified version of recently proposed models for the dynamics of sand piles.

We investigate the motion of a hard cylinder rolling down a soft inclined plane. The cylinder is subjected to a viscous drag force and stochastic fluctuations due to the surrounding medium. In a wide range of parameters we observe bistability of the rolling velocity. In dependence on the parameters, increasing noise level may lead to increasing or decreasing average velocity of the cylinder. The approximative analytical theory agrees with numerical results.

Atomic clusters were identified in the ground state of the non-equilibrium Ta phase (Frank-Kasper σ-structure type) at 15, 120 and 293 K. The evolution of the clusters with temperature leads to two phase transformations at 65 and 150 K which are related to the electrical and magnetic properties. The magnetic phase transition at 65 K is associated with the magnetic symmetry group transformation P4'₂/mn'm ( < 65 K) to P' ( > 65 K). It is shown that β-U is also a two-component composite containing similar clusters. The nature of the stabilisation of β-Ta at the cathode is discussed.

Sm was studied by Raman spectroscopy at pressures up to 20 GPa. The Raman-active phonon modes, both of the Sm-type phase and the dhcp phase, show a frequency decrease as pressure increases. There is evidence that the entire structural sequence hcp → Sm-type → dhcp → fcc under pressure for the individual regular lanthanides is associated with softening of certain acoustic and optical-phonon modes as well as elastic anomalies. Comparison is made to corresponding transitions between close-packed lattices in other metals and possible relations to the lanthanide's electronic structure are addressed.

Analytic expression for the memory function and the optical conductivity of the two-dimensional Bose gas with logarithmic interaction at T = 0 in the presence of point-like impurities is obtained within the mode-coupling approximation. Depending on the value of a dimensionless combination of the model parameters proportional to the strength of the impurity potential, two different phases are distinguished, viz the disordered superfluid and insulator (Bose glass), separated by an intermediate (quasi)metal state.

The mean-field study of the stripe phases of the t-t'-U Hubbard model confirms the formation of the in-gap subbands of states localized on the domain walls. For bond-aligned stripes it is shown that segments of Fermi surfaces in antinodal and nodal directions correspond to the in-gap band or to that delocalized over a whole antiferromagnet domain. This can explain the dichotomy between the corresponding quasiparticles in La_{2 − x}Sr_xCuO₄ (LSCO) and the suppression of spectral weight in the nodal direction in underdoped LSCO. The Fermi surface changes its topology with doping. It is confirmed also that diagonal stripes can provide an insulating state at nonzero doping.

We investigate the energy spectrum and the density of states (DOS) in a 2D triangular tight-binding model with hopping integrals modulated by staggered magnetic fluxes (SMFs). Three different types of SMFs are considered. The SMFs result in shifts of the original Van Hove singularity (VHS) peak in the DOS, or even generate new flux-dependent VHSs. And a gap or a pseudogap can also be generated on the original Fermi surface. The magnitude of the pseudogap or the gap and its symmetries depend on the chemical potential μ, and on the flux parameters.

We report magnetic dichroism in photoemission using linearly polarized synchrotron radiation (XMLD) from the 3p core levels of the ferromagnetic metals Fe, Co, Ni, and their binary alloys, including Cu. Lineshape analysis reveals that the magnetic dichroism asymmetry in the spectral width, W_XMLD, tracks the changing magnitudes of the elemental magnetic moments. In contrast, the magnetic dichroism asymmetry peak-to-peak amplitudes, A_XMLD, monitor the overall saturation magnetization, which shows deviations from the Slater-Pauling curve due to changes in magnetic order, particularly at the Invar composition of Fe₆₅Ni₃₅.

The center-of-mass momentum distribution of optically created excitons in semiconductors is known to be constrained by the (very small) light momenta at times immediately following the excitation, and it is governed by incoherent scattering processes on longer time scales. The present theoretical analysis suggests that, on intermediate time scales, nonlinear mean-field interactions between excitons lead to a coherent, wave-like evolution in the momentum distribution of optically inactive excitons. Proposals for possible experimental verification of these predictions are discussed.

We study the Kondo effect in a quantum dot embedded in a mesoscopic ring taking into account the intradot spin-flip scattering R. Based on the finite-U slave-boson mean-field approach, we find that the Kondo peak in the density of states is split into two peaks by this coherent spin-flip transition, which is responsible for some interesting features of the Kondo-assisted persistent current circulating the ring: 1) strong suppression and crossover to a sine function form with increasing R; 2) appearance of a "hump" in the R-dependent behavior for odd parity. R-induced reverse of the persistent current direction is also observed for odd parity.

In type-I superconducting cylinders, bulk superconductivity is destroyed above the first critical current. Below the second critical current the "type-I mixed state" displays fluctuation superconductivity which contributes to the total current. A magnetic flux on the axis of the cylinder can change the second critical current by as much as 50 percent, so that half a flux quantum can switch the cylinder from normal conduction to superconductivity: the Aharonov-Bohm effect manifests itself in macroscopically large resistance changes of the cylinder.

We study the electron thermal transport in granular metals at large tunnel conductance between the grains, g_T >> 1, and not too low a temperature, T > g_Tδ, where δ is the mean energy level spacing for a single grain. Taking into account the electron-electron interaction effects, we calculate the thermal conductivity and show that the Wiedemann-Franz law is violated for granular metals. We find that interaction effects suppress the thermal conductivity less than the electrical conductivity.

Thin films of alkali metals are forced into an insulating state by being covered with sub-mono-layers of Pb. The superconducting proximity effect is used to investigate the electronic change in the alkali film. On the length scale of the film thickness the electronic properties of the alkali film do not change noticeably during the metal-insulator transition.

We present microscopic estimates for the spin-spin and spin-pseudospin interactions of the quarter-filled ladder compound NaV₂O₅, obtained by exactly diagonalizing appropriate clusters of the underlying generalized Hubbard Hamiltonian. We present evidence for a substantial interladder spin-pseudospin interaction term which would allow simultaneously for the superantiferroelectric (SAF) charge (pseudospin) ordering and spin dimerization. We discuss the values of the coupling constants appropriate for NaV₂O₅ and deduce the absence of a soft antiferroelectric mode.

We report the response of electrical resistivity ρ to the application of magnetic fields (H) up to 140 kOe in the temperature interval 1.8–300 K for the compound Gd₇Rh₃, ordering antiferromagnetically below 150 K. We find that there is an unusually large decrease of ρ for moderate values of H in the close vicinity of room temperature, uncharacteristic of paramagnets, with the magnitude of the magnetoresistance increasing with decreasing temperature as though the spin-order contribution to ρ were temperature dependent. In addition, this compound exhibits giant-magnetoresistance behaviour at rather high temperatures (above 77 K) in the magnetically ordered state due to a metamagnetic transition.

We have evidenced bundle formation in DNA solutions, induced by the addition of a monovalent cationic surfactant to a solution of short DNA rods. The bundles are rod-like, with a large axial ratio ( ∼ 10). Their formation is very likely controlled not only by electrostatic interactions, but also by hydrophobic interactions between surfactant chains, once bound to the DNA. The bundles have diameters and lengths both remarkably well defined and possess internal organisation. The value of the diameter is close to that predicted by a model in which interactions are mediated by condensed counterions; the length might be limited by steric hindrance due to bundle overlapping or by intrinsic chain flexibility.

Two- and three-particle correlation functions are computed from video-microscopy data of two-dimensional suspensions of charged colloids and inverted to derive the pair and three-body interaction potentials between the colloidal particles. Our method allows to resolve the full spatial dependence of the three-body potentials. Examining colloidal systems at different colloid densities, we find density-independent, attractive three-body potentials, with a minimum of a few kT that is most pronounced in the equilateral triangle configuration.

We develop a theory for the full counting statistics (FCS) for a class of nanoelectromechanical systems (NEMS), describable by a Markovian generalized master equation. The theory is applied to two specific examples of current interest: vibrating C₆₀-molecules and quantum shuttles. We report a numerical evaluation of the first three cumulants for the C₆₀ setup; for the quantum shuttle we use the third cumulant to substantiate that the giant enhancement in noise observed at the shuttling transition is due to a slow switching between two competing conduction channels. Especially the last example illustrates the power of the FCS.

Soft interfaces can mediate interactions between particles bound to them. The force transmitted through the surface geometry on a particle may be expressed as a closed line integral of the surface stress tensor around that particle. This contour may be deformed to exploit the symmetries present; for two identical particles, one obtains an exact expression for the force between them in terms of the local surface geometry of their mid-plane; in the case of a fluid membrane the sign of the interaction is often evident. The approach, by construction, is adapted directly to the surface and is independent of its parameterization. Furthermore, it is applicable for arbitrarily large deformations; in particular, it remains valid beyond the linear small-gradient regime.