Table of contents

In this letter we predict a novel second-order quantum phase transition of two-component Bose-Einstein condensates coupled with a periodically driven laser field in the resonant case. It is shown that this quantum phase transition from the normal to the tunneling phases can be controlled by the interspecies nonlinear interaction tuned via the magnetic-field–dependent Feshbach resonance technique. Furthermore, it is also demonstrated that this quantum phase transition can be detected by measuring the ground-state population imbalance between two condensates.

We study the effect of memory on synchronization of identical chaotic systems driven by common external noises. Our examples show that while in general the synchronization transition becomes more difficult to meet when the memory range increases, for intermediate ranges the synchronization tendency of systems can be enhanced. Generally the synchronization transition is found to depend on the memory profile and range and the ratio of noise strength to memory amplitude, which indicates a possibility of optimizing synchronization by memory. We also point out a close link between dynamics with memory and noise, and recently discovered synchronizing properties of networks with delayed interactions.

The validity of the Jarzynski equation for a very simple, exactly solvable quantum system is analyzed. The implications of two different definitions of work proposed in the literature are investigated. The first one derives from measurements of the system energy at the beginning and at the end of the process under consideration making the work a classical stochastic variable with transition probabilities derived from quantum-mechanics. In the second definition an operator of work is introduced and the average in the Jarzynski equation is a quantum expectation value. For the first definition a general quantum-mechanical version of the Jarzynski equation is known to hold. For the second one the Jarzynski equation fails to yield the free energy difference at low temperature.

The topological force and torque are investigated in systems with spin-orbit coupling. It is demonstrated that the topological force and torque appears as a pure relativistic quantum effect in an electromagnetic field. The origin of both topological force and torque is the Zitterbewegung effect. Considering nonlinear behaviors of spin-orbit coupling, we address possible novel phenomena driven by the topological forces.

We predict three different, quite unusual transport properties of an underdamped Brownian particle in the form of current and force of opposite signs. Their origin is a subtle interplay between the stability of coexisting attractors, noise-induced metastability, and transient chaos. Numerical simulations are complemented by intuitive explanations of the basic mechanism and analytical approximations.

Two types of relativistic transformation for the four-vector (ω/c, k) of waves (including light waves in media, or acoustic waves) are obtained based on the differential Lorentz transformation. One of them is just the usual Lorentz transformation, whereas the second one is not. The second one is required to secure the frequency of waves from being negative, in the case that the speed of waves in a medium is less than the speed of that medium moving in the direction opposite to the propagation direction of waves. Therefore, the four-vector (ω/c, k) of waves is in general not Lorentz-covariant. The invariance of the phase of waves among inertial frames is questionable.

Classical ratchets have been recently successfully realized using cold atoms in driven optical lattices. Here we study the current rectification of the motion of a quantum particle in a periodic potential exposed to an external ac field. The dc current appears due to the desymmetrization of Floquet eigenstates, which become transporting. Quantum dynamics enhances the dependence of the current on the initial phase of the driving field. By changing the laser field parameters which control the degree of space-time asymmetry, Floquet eigenstates are tuned through avoided crossings. These quantum resonances induce resonant changes of the resulting current. The width, strength and position of these quantum resonances are tunable using control parameters of the experimental realization with cold atoms.

Using the measured fragmentation cross-sections produced from the ⁴⁸Ca and ⁶⁴Ni beams at 140 MeV per nucleon on ⁹Be and ¹⁸¹Ta targets, we find that the cross-sections of unmeasured neutron-rich nuclei can be extrapolated using a systematic trend involving the average binding energy. The extrapolated cross-sections will be very useful in planning experiments with neutron-rich isotopes produced from projectile fragmentation. The proposed method is general and could be applied to other fragmentation systems including those used in other radioactive ion beam facilities.

Due to the formation of arches, granular materials may jam when flowing through obstacles, as in the case of hoppers. As a way to quantify this process, we study experimentally the flow of binary granular mixtures through sieves, as a function of two parameters: the proportion of large grains and the ratio of large grains to sieve hole size. We distinguish three regimes: steady flows, jamming, and progressive clogging. In the case of steady flows, we measure the dependencies of the flow rate on the two parameters and observe a generalization of the law known for mono-disperse grains flowing through a single aperture. Moreover we measure how the critical size of the holes leading to jamming depends on the proportion of large grains. In the case of progressive clogging, we measure the slowing down of the flow rate and identify two mechanisms associated to the trapping of the large grains in the holes of the sieves and then to the formation of a filtration cake.

A reason has been given for the inverse energy cascade in the two-dimensionalised rapidly rotating 3D incompressible turbulence. For such system, the literature shows a possibility for the wave number exponent in the energy spectrum's relation to lie between −2 and −3. We argue the existence of a stricter range of −2 to −7/3 for the exponent in the case of rapidly rotating turbulence which is in accordance with the recent experiments. Also, a derivation for the two-point third-order structure function has been provided helping one to argue that even with slow rotation one gets, though dominated, a spectrum with the exponent −2.87, thereby hinting at the initiation of the two-dimensionalisation effect with rotation.

This paper models the effects of bandwidth on the traffic capacity of scale-free networks. We investigate the decrease of the system traffic capacity and the variation of the optimal local routing coefficient α_c, induced by the restriction of bandwidth. For low bandwidth, the same optimal value of α_c emerges for two different cases of node capacity, namely C = constant and C_i = k_i, where k_i denotes the degree of the i-th node. By investigating the number of packets at each node in the free-flow state, we provide analytical explanations for the optimal value of α_c. Average packet travelling time, distribution of packet travelling time, and average visits per node divided by the node connectivity are also studied.

The steady-state morphology of submonolayer Si/Si(111)7×7 islands is characterized by a size-dependent transition from compact through ramified to 1D-like forms. The transition is described by the linear-chain model (LCM), which explains this shape transition in strained heteroepitaxial layers, as a mechanism for strain relaxation without dislocations. We found that above the percolation coverage θ_c, the entire structure adopts new steady-state morphology and reduces its typical width by a factor of e, to its optimal-energy value. The LCM predicts this value as the asymptotic behavior for infinite elongated islands. Our experimental results, which are supported by energy calculations, confirm the LCM predictions for the first time in homoepitaxy. These results are explained by a size-dependent mesoscopic mismatch between the islands and the substrate.

We report on a novel simultaneous observation of two inelastic doublets in the dynamic structure factor of the liquid alloy Li₃₀Bi₇₀. This result establishes the coexistence of two density fluctuation modes in a liquid binary system with disparate mass components. The measurements of the dynamic structure factor of the alloy have been performed on the hot neutron three-axis spectrometer IN1 of the Institut Laue-Langevin with an unprecedented energy resolution in the small wave vector domain. Analysis of the dynamical parameters characterizing the two excitations reveals the acoustic nature of the low-frequency mode and suggests an optic-like nature for the high-frequency mode. A comparison with recent neutron scattering results on pure liquid Bi suggests that the low-frequency mode in the alloy is closely related to the heavier component dynamics.

We present a fully microscopic approach to the transition rate of two exciton-photon polaritons. The non-trivial consequences of the polariton composite nature—here treated exactly through a development of our composite-exciton many-body theory—lead to results noticeably different from the ones of the conventional approaches in which polaritons are mapped into elementary bosons. Our work reveals an appealing fundamental scattering which corresponds to a photon-assisted exchange—in the absence of Coulomb process. This scattering being dominant when one of the scattered polaritons has a strong photon character, it should be directly accessible to experiment. In the case of microcavity polaritons, it produces a significant enhancement of the polariton transition rate when compared to the one coming from Coulomb interaction. This paper also contains the crucial tools to securely tackle the many-body physics of polaritons, in particular towards its possible BEC.

Combining the one-dimensional tight-binding Su-Schrieffer-Heeger (SSH) model and the extended Hubbard model (EHM), we investigate the effect of electron-electron interactions on the dynamics of a charged polaron in a conjugated polymer chain, by using a nonadiabatic dynamical method. Both the localization and the velocity of the polaron will vary with the on-site Coulomb interactions U and the nearest-neighbor interactions V. It is found that the local extremum of the stationary velocity of the polaron occurs at U≈2 V (U,V>0). Additionally, the relation between the velocity and the lattice structure of the polaron is shown qualitatively.

The antiferromagnetic molecular finite chain Cr₆ was studied by inelastic neutron scattering. The observed magnetic excitations at 2.6 and 4.3 meV correspond, due to the open boundaries of a finite chain, to standing spin waves. The determined energy spectrum revealed an essentially classical spin structure. Hence, various spin-wave theories were investigated in order to assess their potential for describing the elementary excitations of finite spin systems.

The electric conductance of a strip of undoped graphene increases in the presence of a disorder potential, which is smooth on atomic scales. The phenomenon is attributed to impurity-assisted resonant tunneling of massless Dirac fermions. Employing the transfer matrix approach we demonstrate the resonant character of the conductivity enhancement in the presence of a single impurity. We also calculate the two-terminal conductivity for the model with one-dimensional fluctuations of disorder potential by a mapping onto a problem of Anderson localization.

We have used a non-magnetic Al₂O₃ barrier, impregnated in (La_0.5Pr_0.2)Sr_0.3MnO₃ (LPSMO) thin film layers, to obtain large magnetoresistance (MR) in the vicinity of room temperature. In the magnetic field of 1T, the LPSMO/Al₂O₃/LPSMO heterostructure exhibits an MR of ∼35% at its insulator-to-metal transition temperature (T_IM) of ∼220 K vis-à-vis an MR of ∼8% in the pristine LPSMO film at its T_IM of 298 K. This enhanced MR, coupled with a 2- to 3-fold increase in the temperature coefficient of resistance and the field coefficient of resistance in the heterostructure compared to that in the LPSMO films, demonstrates the efficiency of this technique in engineering those physical properties of manganites which have potential bearing on the realization of their technological applications.

The heavy-electron superconductor CeCoIn₅ exhibits a puzzling precursor state above its superconducting critical temperature at T_c=2.3 K. The thermopower and Nernst signal are anomalous. Below 15 K, the entropy current of the electrons undergoes a steep decrease reaching ∼0 at T_c. Concurrently, the off-diagonal thermoelectric current α_xy is enhanced. The delicate sensitivity of the zero-entropy state to field implies phase coherence over large distances. The prominent anomalies in the thermoelectric current contrast with the relatively weak effects in the resistivity and magnetization.

We found the mechanism of how a silica-particle–reinforced elastomer after being sheared in oscillation at a strain could produce a spectrum hole or a drop in its dissipation spectrum at that amplitude, but not at other amplitudes. We also found that sequential holding the system at two strains could produce one or two holes depending on the deformation histories. When the second holding strain was higher than the first, the effect of hole burning of only high strain was evident, whereas the effects of hole burning at both strains were revealed when the second strain was lower than the first. This unexpected discovery suggests that the structural relaxations of a particle-suspension system are heterogeneous, and shearing at a fixed strain only affects part of its relaxation spectra.

We study the translocation dynamics of a polymer chain threaded through a nanopore by an external force. By means of diverse methods (scaling arguments, fractional calculus and Monte Carlo simulation) we show that the relevant dynamic variable, the translocated number of segments s(t), displays an anomalous diffusive behavior even in the presence of an external force. The anomalous dynamics of the translocation process is governed by the same universal exponent α=2/(2ν+2−γ₁), where ν is the Flory exponent and γ₁ the surface exponent, which was established recently for the case of non-driven polymer chain threading through a nanopore. A closed analytic expression for the probability distribution function W(s, t), which follows from the relevant fractional Fokker-Planck equation, is derived in terms of the polymer chain length N and the applied drag force f. It is found that the average translocation time scales as . Also the corresponding time-dependent statistical moments, and reveal unambiguously the anomalous nature of the translocation dynamics and permit direct measurement of α in experiments. These findings are tested and found to be in perfect agreement with extensive Monte Carlo (MC) simulations.

We study the bromide counterion distribution near a solid-supported monolayer in the case of vanishing bulk electrolyte concentration by resonant X-ray reflectivity. The surface charge density of the monolayer was varied by using different molar ratios of the cationic Di-Octadecyl-Di-methyl-Ammonium-Bromide (DODAB) and the neutral Di-Palmitoyl-Glycero-Phosphocholine (DPPC). The analysis, either based on a conventional box model with an additional counterion contribution, or based on an independent unbiased global optimization approach, yields a good agreement with the classical Poisson-Boltzmann theory for the salt-free case.

I apply the recently proposed intermittence strategy to investigate the ancient human migrations in the world. That is, the Americas colonization (Bering-bridge and Pacific-coast theories) and Neanderthal replacement in Europe around 45000 years before the present. Using a mathematical equation related to diffusion and ballistic motion, I calculate the colonization time in all these cases in good agreement with archeological data (including Neolithic transition in Europe). Moreover, to support these calculations, I obtain analytically the effective speed of colonization in Europe v_eff=0.62 [km/yr] and related to the Aurignacian culture propagation.

A quantum spin model representing tautomeric mutation is proposed for any DNA molecule. Based on this model, the quantum-mechanical calculations for mutational rate and complementarity restoring repair rate in the replication processes are carried out. A possible application to a real biological system is discussed.