International Journal of Modern Physics B

We have studied the single-particle heat engine and refrigerator driven by time-asymmetric protocol of finite duration. Our system consists of a particle in a harmonic trap with time-periodic strength that drives the particle cyclically between two baths. Each cycle consists of two isothermal steps at different temperatures and two adiabatic steps connecting them. The system works in irreversible mode of operation even in the quasistatic regime. This is indicated by finite entropy production even in the large cycle time limit. Consequently, Carnot efficiency for heat engine or Carnot coefficient of performance (COP) for refrigerators is not achievable. We further analyzed the phase diagram of heat engines and refrigerators. They are sensitive to time-asymmetry of the protocol. Phase diagram shows several interesting features, often counterintuitive. The distribution of stochastic efficiency and COP is broad and exhibits power-law tails.

In the network of self-driven particles, aggregation points make velocities of particles smaller and branching points make larger. We consider a ladder-shaped network of totally asymmetric simple exclusion process in order to investigate correlations among multiple junctions by extending our previous results about “critical ellipse” which is the condition where the congestion of particles near the aggregation point propagates to the upstream of the branching point. We have theoretically derived the condition of interactions among the congestion from different aggregation points in the network.

We report the structural, electronic, optical, and thermoelectric properties of the five cubic alkali-earth transition-metals AZn${}_{13}$ (A-Na, K, Ca, Sr, Ba) using density functional theory. Structural properties, electronic structures and optical behaviors are calculated explicitly via highly accurate contemporary full potential-linearized augmented plane wave (FP-LAPW) method. The investigated ground state data of these materials is quite close to the experimental information. The modified Becke–Johnson (mBJ) predicts the intermetallic nature of AZn${}_{13}$ (A-Na, K, Ca, Sr, Ba) materials. The complex dielectric function of these intermetallic compounds has been calculated and the observed noticeable peaks are examined through mBJ. With the help of complex dielectric function, the other important optical parameters like reflectivities, conductivities and refractive indices of AZn${}_{13}$ (A-Na, K, Ca, Sr, Ba) have been calculated as a function of energy. The optical response suggests that AZn${}_{13}$ (A-Na, K, Ca, Sr, Ba) compounds can be used for the optoelectronic devices. Further, the thermoelectric properties have been calculated through BoltzTraP program, the calculated values for different thermoelectric parameters recommend that these AZn${}_{13}$ (A-Na, K, Ca, Sr, Ba) materials are the suitable candidates for thermoelectric applications.

The link prediction algorithm is one of the key technologies to reveal the inherent rule of network evolution. This paper proposes a novel link prediction algorithm based on the properties of the local community, which is composed of the common neighbor nodes of any two nodes in the network and the links between these nodes. By referring to the node degree and the condition of assortativity or disassortativity in a network, we comprehensively consider the effect of the shortest path and edge clustering coefficient within the local community on node similarity. We numerically show the proposed method provide good link prediction results.

Using classical ensemble method, we have investigated the pulse duration dependence of sequential double ionization (SDI) of Ar atoms driven by circularly polarized laser pulses. The results show that the ion momentum distribution of Ar atoms depends strongly on the pulse duration. As the pulse duration increases, the ion momentum distribution changes from single-ring to double-ring structure, and finally to the single-ring structure. Back analysis of double ionization trajectories shows that the variation of the ring structure originates from the dependence of the ionization time of the second electron on the pulse duration. Moreover, our calculations clearly manifest the subcycle electron emission in sequential double ionization by circularly polarized laser pulses.

In this work, we investigate some aspects of the confinement problem in Möbius strips in the context of the low-energy approximation of graphene, aiming to provide an analytical prescription for studying graphene-based nanoribbons in response to the peculiar background proper to such objects. Based on a topological treatment, we model the confinement of massless Dirac fermions in such nanostructures by proposing boundary conditions capable of incorporating their typical topological character, and examine how such configuration affects the physical properties of graphene. Energy eigenvalues are found to be sensitive to the transverse confinement and the positions along the transverse direction, exhibiting an unexpected spatial constraint. In addition, a dual electronic behavior associated with this aspect is also suggested under certain limits within our solution, which includes the presence of a length-dependent gap that responds to the longitudinal boundary conditions. At the same time, we look at the problem from a more mathematical perspective and sketch out some insights into the role played by the notion of self-adjointness in such boundary problem. A peculiar position constraint acts on our solution and manifests itself as partial restriction on the proposed set, pointing to the definition of incomplete domain self-adjoint extensions as well as to the nonexistence of conventional Möbius periodicities compatible with infinite mass confinement.

First-principles calculations of the electronic structure of substitutional rare earth (RE) impurity (Eu and Gd) in wurtzite ZnO have been performed using density functional theory within a Hubbard potential correction to the RE 4f states. For Eu-doped ZnO, the magnetic coupling between Eu ions in the nearest neighbor sites is ferromagnetic (FM). The room temperature (RT) ferromagnetism (FM) can be enhanced by an appropriate hole doping into the sample. The ZnO:Gd is found to favor the antiferromagnetic (AFM) phase. The FM can be achieved by high electron doping. The native defects effect (V${}_{\mathrm{\text{O}}}$, V${}_{\mathrm{\text{Zn}}}$) on the FM is also studied. The oxygen vacancies seem to play an important role in the generation of the FM in both ZnO:Eu and ZnO:Gd, which is in good agreement with recent experimental results.

We consider a conduction electron that couples with the localized spins, which are close to the antiferromagnetic ordered state. We show that the hopping of the conduction electron is possible even if the neighboring spins are almost antiparallel, and the difference in the relative angles between the neighboring spins leads to anisotropic diffusion of the conduction electron. Our calculation supports the presence of the spinmotive force in antiferromagnets.

In this paper, a unified model is presented for two-lane lattice traffic flow, with comparing different effects in the various lattice hydrodynamic models. Results of linear and nonlinear analysis show that multiple density difference effect (MDDE) is the strongest to enlarge the stable region in two-lane systems. Followed by density difference effect (DDE), multiple flux difference effect (MFDE), and finally flux difference effect (FDE). But when density is around 0.25, MFDE is better to enlarge the stable region than DDE. The reason is that a small flow-rate value might correspond to either a light traffic or a heavy traffic. Also energy consumption and traffic emissions are analyzed and shown to be the same marshaling sequence as linear and nonlinear analysis results. Numerical simulations validate theoretical analysis. And this is consistent with the realistic.

This paper reports the first-principles study of SnO under high pressure within the generalized gradient approximation (GGA). We have calculated the structural, elastic, electronic and optical properties of SnO. The elastic properties such as the elastic constants $C_{ij}$, bulk modulus, shear modulus, Young’s modulus, anisotropic factor, Pugh’s ratio and Poisson’s ratio are calculated and analyzed. Mechanical stability of SnO at all pressures is confirmed using the Born’s stability conditions in terms of $C_{ij}$. It is also found that SnO exhibits very high anisotropy. The energy band structure and density of states are also calculated and analyzed. The results show the semiconducting and metallic properties at zero and high pressures, respectively. Furthermore, the optical properties are also calculated. All the results are compared with those of SnO where available but most of the results at high pressure are not compared due to the unavailability of results.

We present a systematic study of high-order harmonic generation (HHG) from helium ion with the initial state prepared as a coherent superposition of electronic ground state and an excited state. As a result, the conversion efficiency of the harmonic spectrum is significantly enhanced. When we add a static electric field in fundamental field, the supercontinuum region of the harmonic spectrum is distinctly extended and an isolated 100 as pulse can be generated. Moreover, we use a spatial nonhomogeneous field to increase the cutoff energy in high-order harmonic generation spectrum, which can be extended to about 700 eV, and an isolated 50 as pulse can be obtained directly by the superposition of the supercontinuum harmonics.