Table of contents

It is generally thought that the adiabatic exchange of two identical particles is impossible in one spatial dimension. Here we describe a simple protocol that permits the adiabatic exchange of two Majorana fermions in a one-dimensional topological superconductor wire. The exchange relies on the concept of "Majorana shuttle" whereby a π domain wall in the superconducting order parameter which hosts a pair of ancillary majoranas delivers one zero mode across the wire while the other one tunnels in the opposite direction. The method requires some tuning of parameters and does not, therefore, enjoy full topological protection. The resulting exchange statistics, however, remain non-Abelian for a wide range of parameters that characterize the exchange.

About a dozen measurements of Newton's gravitational constant, G, since 1962 have yielded values that differ by far more than their reported random plus systematic errors. We find that these values for G are oscillatory in nature, with a period of $P = 5.899 \pm 0.062\ \text{yr}$, an amplitude of $(1.619 \pm 0.103) \times 10^{-14}\ \text{m}^3\ \text{kg}^{-1}\ \text{s}^{-2}$, and mean-value crossings in 1994 and 1997. However, we do not suggest that G is actually varying by this much, this quickly, but instead that something in the measurement process varies. Of other recently reported results, to the best of our knowledge, the only measurement with the same period and phase is the Length of Day (LOD —defined as a frequency measurement such that a positive increase in LOD values means slower Earth rotation rates and therefore longer days). The aforementioned period is also about half of a solar activity cycle, but the correlation is far less convincing. The 5.9 year periodic signal in LOD has previously been interpreted as due to fluid core motions and inner-core coupling. We report the G/LOD correlation, whose statistical significance is 0.99764 assuming no difference in phase, without claiming to have any satisfactory explanation for it. Least unlikely, perhaps, are currents in the Earth's fluid core that change both its moment of inertia (affecting LOD) and the circumstances in which the Earth-based experiments measure G. In this case, there might be correlations with terrestrial-magnetic-field measurements.

We discuss how maximum entropy methods may be applied to the reconstruction of Markov processes underlying empirical time series and compare this approach to usual frequency sampling. It is shown that, in low dimension, there exists a subset of the space of stochastic matrices for which the MaxEnt method is more efficient than sampling, in the sense that shorter historical samples have to be considered to reach the same accuracy. Considering short samples is of particular interest when modelling smoothly non-stationary processes, which provides, under some conditions, a powerful forecasting tool. The method is illustrated for a discretized empirical series of exchange rates.

Using Brownian dynamics (BD) simulations we investigate the non-equilibrium structure formation of a two-dimensional (2D) binary system of dipolar colloids propelling in opposite directions. Despite a pronounced tendency for chain formation, the system displays a transition towards a laned state reminiscent of lane formation in systems with isotropic repulsive interactions. However, the anisotropic dipolar interactions induce novel features: First, the lanes have themselves a complex internal structure characterized by chains or clusters. Second, laning occurs only in a window of interaction strengths. We interpret our findings by a phase separation process and simple force balance arguments.

We show that a quantum walk process can be used to construct and secure quantum memory. More precisely, we show that a localized quantum walk with temporal disorder can be engineered to store the information of a single, unknown qubit on a compact position space and faithfully recover it on demand. Since the localization occurs with a finite spread in position space, the stored information of the qubit will be naturally secured from the simple eavesdropper. Our protocol can be adopted to any quantum system for which experimental control over quantum walk dynamics can be achieved.

We present a general formalism for computing the largest Lyapunov exponent and its fluctuations in spatially extended systems described by diffusive fluctuating hydrodynamics, thus extending the concepts of dynamical system theory to a broad range of non-equilibrium systems. Our analytical results compare favourably with simulations of a lattice model of heat conduction. We further show how the computation of the Lyapunov exponent for the symmetric simple exclusion process relates to damage spreading and to a two-species pair annihilation process, for which our formalism yields new finite-size results.

We continue the discussion on the interaction energy of the axially symmetric hopfions evaluated directly from the product anzsatz. The hopfions are given by the projection of Skyrme model solutions onto the coset space $SU(2)/U(1)$. Our results show that if the separation between the constituents is not small, the product ansatz can be considered as a good approximation to the general pattern of hopfions interaction both in repulsive and attractive channels.

We show in detail that the Parikh-Wilczek tunneling method (PWTM), which was designed for resolving the information loss problem in Hawking radiation (HR) fails whenever the radiation occurs from an isothermal process. The PWTM aims to produce a non-thermal HR which adumbrates the resolution of the problem of unitarity in quantum mechanics (QM), and consequently the entropy (or information) conservation problem. The effectiveness of the method has been satisfactorily tested on numerous black holes (BHs). However, it has been shown that the isothermal HR, which results from the emission of the uncharged particles of the linear dilaton BH (LDBH) described in the Einstein-Maxwell-Dilaton (EMD) theory, the PWTM has vulnerability in having non-thermal radiation. In particular, we consider Painlevé-Gullstrand coordinates (PGCs) and isotropic coordinates (ICs) in order to prove the aforementioned failure in the PWTM. While carrying out calculations in the ICs, we also highlight the effect of the refractive index on the null geodesics.

We theoretically study the cyclotron dynamics of ultra-cold atoms in optical lattices exposed to an artificial magnetic field. The cyclotron orbit and its stability are discussed both analytically and numerically. We find that the cyclotron dynamics of atoms in optical lattices can be manipulated by adjusting the strength of the magnetic field. Atoms can be coherently localized in its initial position, or can be trapped in a priori prescribed orbit doing coherent cyclotron motion, or can be decoherently diffused with time. The stability of the orbit and the coherence of the system present asymmetric characters. Our results provide a direct theoretical evidence for the cyclotron dynamics of neutral atoms in the artificial magnetic field.

By using a simple statistical model we find the distribution of scar intensities surviving the semiclassical limit. The obtained distribution is verified in a wide energy range of the quantum Bunimovich stadium billiard.

The modified Coulomb-Born approximation including the proton impact internuclear interaction (MCB-PI) is applied to study single ionization of helium by 75 keV proton impact. Fully differential cross-sections (FDCS) are calculated both in the scattering and perpendicular planes. The results are compared with experimental data and theoretical predictions from the three-body distorted wave (3DW) and the continuum distorted wave-eikonal initial state (CDW-EIS). It is shown that the features of the FDCS are better reproduced by the MCB-PI results. We also assess the influence of the PI interaction on the FDCS and we find that the PI interaction is particularly important in the perpendicular plane.

Nanophotonics is a multidisciplinary frontier of science that merges nanoscience and nanotechnology with conventional optics and photonics. We focus on two principal issues of nanophotonics: manipulation of optical field and light-matter interaction via various optical nanostructures. These two issues are behind all the efforts to explore, design, and build nanophotonic devices to accomplish the fundamental cause of large-scale optical integration for information processing, interconnection, and computing. We discuss various mechanisms of light-matter interaction enhancement to realize bright fluorescence, Raman, and nonlinear optical radiation, and explore methodologies and various devices for highly sensitive optical sensing and detecting, ultrahigh spatial resolution imaging, and high-efficiency energy conversion between light and electricity, heat, and other forms. All these concepts, insights, methodologies, and technologies in nanophotonics will set a solid platform to explore and achieve better future information and energy technologies that use light as powerful information and energy carriers and as prominent media to probe and manipulate the intrinsic properties of matters via light-matter interaction.

Here we report the creation and observation of acoustic vortices of fractional order. Whilst integer orders are known to produce axisymmetric acoustic fields, fractional orders are shown to break this symmetry and produce a vast array of unexplored field patterns, typically exhibiting multiple closely spaced phase singularities. Here, fractional acoustic vortices are created by emitting ultrasonic waves from an annular array of sources using multiple ramps of phase delay around its circumference. Acoustic radiation force patterns, including multiple concentration points, short straight lines, triangles, squares and discontinuous circles are simulated and experimentally observed. The fractional acoustic vortex leading to two closely spaced phase singularities is used to trap, and by controlling the order, reversibly manipulate two microparticles to a proximity of 0.3 acoustic wavelengths.

The ABC flow was originally introduced by Arnol'd to investigate Lagrangian chaos. It soon became the prototype example to illustrate magnetic-field amplification via fast dynamo action, i.e. dynamo action exhibiting magnetic-field amplification on a typical timescale independent of the electrical resistivity of the medium. Even though this flow is the most classical example for this important class of dynamos (with application to large-scale astrophysical objects), it was recently pointed out (Bouya Ismaël and Dormy Emmanuel, Phys. Fluids, 25 (2013) 037103) that the fast dynamo nature of this flow was unclear, as the growth rate still depended on the magnetic Reynolds number at the largest values available so far $(\text{Rm} = 25000)$. Using state-of-the-art high-performance computing, we present high-resolution simulations (up to 4096³) and extend the value of $\text{Rm}$ up to $5\cdot10^5$. Interestingly, even at these huge values, the growth rate of the leading eigenmode still depends on the controlling parameter and an asymptotic regime is not reached yet. We show that the maximum growth rate is a decreasing function of $\text{Rm}$ for the largest values of $\text{Rm}$ we could achieve (as anticipated in the above-mentioned paper). Slowly damped oscillations might indicate either a new mode crossing or that the system is approaching the limit of an essential spectrum.

The time evolution of temperatures of anisotropic nanoparticles in two- and three-body systems are simulated for various relative orientations. Nanoparticles are immersed in a thermal bath at constant temperature. It is shown that in two-body systems, the relative orientation of nanoparticles could drastically affect the dynamics of temperature evolution and thermalization time scale. Moreover, in some configurations, the temperature difference in initial state has a major effect on the dynamics of temperatures. In three-body systems, the orientation of the third nanoparticle influences the temperature dynamics, which allows one to control the thermalization time scales between anisotropic nanoparticles. Also, in addition to the previously known contribution of the smallest distance between isotropic nanoparticles on the thermalization time scales, it is shown that the nanoparticles' orientations are more important in some particular arrangements.

This paper presents the simulation and experimental results of charged microparticles dynamics in electrodynamic traps in a gas flow at atmospheric pressure. For the first time the capture and confinement of charged microparticles in a linear Paul trap has been experimentally confirmed at atmospheric pressure in gas flows. The regions of the microparticle, linear Paul trap and gas flow parameters needed for microparticle confinement have been obtained and experimentally tested.

Plasmas are known as the most abundant form of matter in the Universe. Nowadays, with respect to the cosmic plasmas, considerable efforts have been put into investigating the experimentally relevant Korteweg-de Vries (KdV)-Burgers–type equations. In this letter, with plenty of experimental/observational support presented, symbolic computation on a general variable-coefficient KdV-Burgers equation is performed, which covers the models for a variety of the cosmic plasmas. An auto-Bäcklund transformation is constructed out, along with two families of the analytic solitonic solutions, for the electrostatic wave potential, perturbation of the magnitude of the magnetic field, fluctuation of electron or ion density, or radial-direction component of the velocity of ions or dust particles. Both our auto-Bäcklund transformation and solitonic solutions depend on the cosmic-plasma parameters by way of the nonlinearity, dispersion, dissipation and geometric-effect coefficient functions, as to the ion-acoustic, magnetoacoustic, electron-acoustic, positron-acoustic, dust-acoustic and quantum dust-ion-acoustic waves. The shock structures from our analytic investigation agree well with to those experimentally reported. Certain effects of a cosmic-plasma system, described by such variable coefficients, might be detected by the future plasma experiments/observations.

The formation of clouds of dust nano-particles in a spherical dc glow discharge in ethanol was observed. Nano-particles were formed in a process of coagulation of ethanol dissociation products in a plasma of gas discharge. During the process the particles were captured into clouds in the electric potential wells of the strong striations of a spherical discharge. Periodically, the cloud of nano-particles experienced some sudden instability (explosion), and started to move to the cathode at high velocity. It was proved that the velocity of the particle clouds was an exponentially decaying function of time as in the case of dissipative dust solitary waves.

We study the electromigration-induced drift of monolayer Ag islands on Ag(111) which contain one Cu atom. For this purpose a three-dimensional self-learning kinetic Monte Carlo model was extended, and a realistic many-body potential was used. The only free parameters of the model are the effective valences of the Ag and Cu atoms. Due to the impurity, the island drift is significantly reduced, especially for small islands. This is traced back to sequential pinning and depinning events, which are analyzed in detail. Surprisingly, this phenomenon is qualitatively independent of the impurity's effective valence, as long as the impurity does not detach from the island edge. How strongly the drift velocity is reduced depends on the effective valence.

We consider two-dimensional $(d=2)$ systems with short-ranged microscopic interactions, where interface unbinding (wetting) transitions occur in the limit of vanishing temperature T. For T = 0 the transition is characterized by non-universal critical properties analogous to those established for thermal wetting transitions in d = 3, albeit with a redefined capillary parameter $\tilde{\omega}$. Within a functional renormalization-group treatment of an effective interfacial model, we compute the finite-temperature phase diagram, exhibiting a line of interface unbinding transitions, terminating at T = 0 with an interfacial quantum-critical point. We identify distinct scaling regimes, reflecting the interplay between quantum and thermal interfacial fluctuations. A crossover line marking the onset of the quantum-critical regime is described by the d = 3 interfacial correlation-length exponent $\nu_{||}$. This potentially opens another way to investigate the non-universal character of $\nu_{||}$. On the other hand, the emergent interfacial quantum-critical regime shows no signatures of non-universality.

Employing Wilson's renormalization group scheme, we investigate the critical behaviour of a modified Ginzburg-Landau model with a nonlocal mode-coupling interaction in the quartic term. Carrying out the calculations at one-loop order, we obtain the critical exponents in the leading order of $\epsilon=4-d-2\rho$, where ρ is an exponent occurring in the nonlocal interaction term and d is the space dimension. Interestingly, the correlation exponent η is found to be non-zero at one-loop order and the expansion corresponds to an expansion about the tricritical mean-field theory in three dimensions, unlike the conventional $\Phi^4$ theory. The ensuing critical exponents are in good agreement with experimental values for samples close to tricriticality. Our analysis indicates that tricriticality is a feature only in three dimensions.

We study swift-heavy-ion track formation in α-quartz using the two-temperature molecular dynamics (2T-MD) model realised as a concurrent multiscale scheme. We compare the simulated track radii to the existing experimental ones obtained from small-angle X-ray scattering and Rutherford backscattering experiments. The 2T-MD model provides an explanation of the origin of the track radii saturation at high electronic stopping power. Furthermore, we study the track structure and show that defects formed outside the region of density fluctuations after a swift-heavy-ion impact may explain the conflicting track radii produced by the two experimental techniques.

We studied the layer-resolved electronic structure of a typical topological insulator, Bi₂Se₃, employing the density functional theory and discovered that the Dirac states primarily consist of the states at the interface of surface and sub-surface quintuple layers in the pristine material instead of the major surface character expected for such systems. The emergence of these states depends strongly on the surface terminations. The surface character of the Dirac states becomes most prominent on the oxygen-deposited Bi-terminated surface due to the change in covalency by the relatively more electronegative oxygen atoms.

We study magnetism in simple models for rare-earth quasicrystals, by considering Ising spins on a quasiperiodic tiling, coupled via RKKY interactions. Computing these interactions from a tight-binding model on the tiling, we find that they are frustrated and strongly dependent on the local environment. Although such features are often associated with spin glass behaviour, we show using Monte Carlo simulations that the spin system has a phase transition to a low-temperature state with long-range quasiperiodic magnetic order.

By means of first-principles calculations, we investigate the electronic structure, lattice dynamics, and electron-phonon coupling of the newly discovered silicide superconductor Li₂IrSi₃. The band structure shows obvious three-dimensional character, and the number of hole pockets around the center of the Brillouin zone depends on whether spin-orbit coupling is taken into consideration. For the phonon-related properties, a phononic-crystal–like behavior with a frequency gap in the range $400\ \text{cm}^{-1} < \omega < 411\ \text{cm}^{-1}$ is discovered, which makes Li₂IrSi₃ a good candidate for controlling the propagation of phonons. The electron-phonon coupling constant λ equals 0.52, and the estimated superconducting transition temperature $T_{c}\simeq 4.1\ \text{K}$ is close to its experimental value, suggesting that Li₂IrSi₃ is a weak-coupling phonon-mediated superconductor.

We present quantum control techniques to engineer flat bands of symmetry-protected Majorana edge modes in s-wave superconductors. Specifically, we show how periodic control may be employed for designing time-independent effective Hamiltonians, which support Floquet Majorana flat bands, starting from equilibrium conditions that are either topologically trivial or only support a Majorana pair per edge. In the first approach, a suitable modulation of the chemical potential simultaneously induces Majorana flat bands and dynamically activates a pre-existing chiral symmetry which is responsible for their protection. In the second approach, the application of effective parity kicks dynamically generates a desired chiral symmetry by suppressing chirality-breaking terms in the static Hamiltonian. Our results demonstrate how the use of time-dependent control enlarges the range of possibilities for realizing gapless topological superconductivity, potentially enabling access to topological states of matter that have no known equilibrium counterpart.

Persistent current is investigated in a zigzag hexagonal graphene ring threaded by a magnetic flux at nonzero temperature. A simple model is introduced which takes into account the electron scattering by phonons. Below room temperature, the phonon energy is extremely smaller than the electron kinetic energy as well as the electron-hole symmetry is present. Because of these, the Aharonov-Bohm oscillations and the persistent current are less affected by the electron-phonon interaction even at room temperature. Above room temperature, there is a strong electron-phonon interaction, which leads to the reduction of the persistent current.

Pentacene/lead phthalocyanine (PbPc)-based isotype and fullerene $(\text{C}_{60})$/PbPc-based anisotype planar heterojunction near-infrared photoresponsive organic field-effect transistors (PhOFETs) were fabricated. We compared the performance of the isotype planar heterojunction PhOFET and the anisotype one, and dominantly investigated the effect of contact on the performance of the isotype planar heterojunction devices. The results showed that the isotype planar heterojunction device exhibits a comparable maximum photoresponsivity $(R_{\textit{max}})$ of 107 mA/W and a comparable maximum photo/dark current ratio $(P_{\textit{max}})$ of $1.4 \times 10^{4}$ to the anisotype one ($R_{\textit{max}}$ of 109 mA/W and $P_{\textit{max}}$ of $1.2 \times 10^{4}$), and exhibits superior air stability to the anisotype one. Moreover, it is surprising to find that Ag source-drain electrodes replacing Au ones yield a performance enhancement in isotype PHJ devices, this is mainly because the use of Ag source-drain electrodes enhances the photo-generated exciton dissociation efficiency at the metal/PbPc interface.

The O₂ dissociation and O₂-dissociation–induced O atoms adsorption on free-standing germanane are studied by using first-principles calculations in this letter. In comparison to the extremely active silicene or silicane with energy barrier of 0.26 eV in oxygen, germanane is more stable than silicene or silicane from the kinetic point of view. Moreover, the most favorable adsorption of O atom on germanene is different to that on silicene or silicane, resulting in a strong OH-group on the germanane surface. Furthermore, the migration and desorption of O atoms are very difficult under room temperature in the O-adsorbed germanane, which is in favor of forming germoxene. The results provide convincing theoretical evidence to show that free-standing gemanane is relatively stable in oxygen,which is different to silicene essentially.

We have found that strong superchiral fields created by surface plasmon resonance exist in hot spots of nonchiral plasmonic structure, which showed a chiral density greater than that of circularly polarized light by hundreds of times. We have demonstrated a direct correlation between the chirality of the local field and the circular dichroism (CD) response at the plasmon resonance bands induced by chiral molecules in the hot spots. Our results reveal that the wavelength-dependent superchiral fields in the hot spots can play a crucial role in the determination of the plasmonic CD effect. This finding is in contrast to the currently accepted physical model in which the electromagnetic field intensity in hot spots is a key factor to determine the peak intensity of the plasmonic CD spectrum. Some related experimental phenomena have been explained by using our theoretical analysis.

The thermodynamical stability of a set of circular double helical molecules is analyzed by path integral techniques. The minicircles differ only in i) the radius and ii) the number of base pairs (N) arranged along the molecule axis. Instead, the rise distance is kept constant. For any molecule size, the computational method simulates a broad ensemble of possible helicoidal configurations while the partition function is a sum over the path trajectories describing the base pair fluctuational states. The stablest helical repeat of every minicircle is determined by free-energy minimization. We find that, for molecules with N larger than 100, the helical repeat grows linearly with size and the twist number is constant. On the other hand, by reducing the size below 100 base pairs, the double helices sharply unwind and the twist number drops to one for N = 20. This is predicted as the minimum size for the existence of helicoidal molecules in the closed form. The helix unwinding appears as a strategy to release the bending stress associated to the circularization of the molecules.

Filament-based intracellular transport involves the collective action of molecular motor proteins. Experimental evidences suggest that microtubule (MT) filament bound motor proteins such as kinesins weakly interact among themselves during transport and with the surrounding cellular environment. Motivated by these observations we study a driven lattice gas model for collective unidirectional transport of molecular motors on open filament. This model incorporates short-range next-nearest-neighbour (NNN) interactions between the motors and couples the transport process on filament with surrounding cellular environment through adsorption-desorption Langmuir kinetics (LK) of the motors. We analyse this model within the framework of a mean-field (MF) theory in the limit of weak interactions between the motors. We point to the mapping of this model with the non-conserved version of the Katz-Lebowitz-Spohn (KLS) model. The system exhibits rich phase behavior with a variety of inhomogeneous phases including localized shocks in the bulk of the filament. We obtain the steady-state density and current profiles, analyse their variation as a function of the strength of interaction and construct the non-equilibrium MF phase diagram. We compare these MF results with Monte Carlo simulations and find that the MF analysis shows reasonably good agreement with simulation results as long as the motors are weakly interacting. For sufficently strong NNN interaction between the motors, the mean-field results deviate significantly, and for very strong NNN interaction in the absence of LK, the current in the lattice is determined solely by the NNN interaction parameter and it becomes independent of entry and exit rates of motors at the filament boundaries.

Using high-resolution magnetic-field Cluster observations, we have investigated the magnetic-field anisotropy via the second- and fourth-order structure functions over a wide range of scales reaching below the subproton scale. The magnetic-field increments have been computed from single- and two-spacecraft measurements. The two-satellite technique allows us to study the increments as a function of an actual space lag. Both single- and two-point analyses show that the magnetic field is anisotropic even at small time/spatial scales. The single-spacecraft data also shows that the degree of anisotropy does not change with the scale at proton and subproton scales. It is also pointed out that the degree of magnetic-field anisotropy tends to be overestimated in the single-spacecraft data analysis. This is particularly evident at small scales and it depends on the angle between the spacecraft separation and the flow direction. From the fourth-order moment of the probability density function of the magnetic-field increments we have also investigated the presence of intermittency in the fluctuations. Even though to a different degree, intermittency was present over the entire range of scales, with an indication of scale invariance at subproton scales.

Self-organization and self-avoiding limit cycles Chaotic explosions Plasma density evolution in a microwave pulse compressor Non-collinear antiferromagnets and the anomalous Hall effect