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Volume 8, Number 1
The electric transport properties of low-dimensional systems have attracted tremendous interests due to their applications in microelectronics and novel nanodevices. Ultra-thin metal films on semiconductor substrates have been a playground for the study of electronic transport properties of low dimensional materials. However, the experimental measurements on the electric transport of such systems are still challenging since they only survive in UHV environments due to high chemical activity. Besides, surface-sensitive methods are required to avoid the substrate effects that could be coupled with the transport of the metal systems atop. We develop the micro-four-point-probe method integrated with standard low-temperature scanning tunneling microscope, which allows the vibration-proof environments and a broad temperature range (4－300 K) for transport measurements. Both the high-resolution characterizations of the surface structure and in situ measurements of the electric transport are realized in a broad temperature range. Taking the Ag/Si(111)-(√3×√3)R30o interface as the prototype of two-dimensional metals, the metal-insulator transition is studied in detail. The surface structure characterizations show hexagonal patterns at room temperature, which supports the model of inequivalent triangle structure. A metal-insulator transition occurs at ~115 K. The low temperature transport measurements clearly reveal the strong localization characteristics of the insulating phase. For more detailed information, please refer to the article “Strong localization across the metal-insulator transition at the Ag/Si(111)-(√3 ×√3)R30o interface” by Yuan-Yuan Tang and Jian-Dong Guo, pp 44–49. [Photo credits: Jian-Dong Guo, Institute of Physics, CAS]
Chun-Zhen Fan, Er-Jun Liang, Ji-Ping Huang
We review the recent theoretical study on the optical properties of one-dimensional soft photonic crystals (1D SPCs) with ferrofluids. The proposed structure is composed of alternating ferrofluid layers and dielectric layers. For the ferrofluid, single domain ferromagnetic nanoparticles can align to a chain under the stimuli of an external magnetic field, thus changing the microstructure of the system. Meanwhile, nonlinear optical responses in ferrofluids are also briefly reviewed.
Xiao-Long Su, Shu-Hong Hao, Ya-Ping Zhao, Xiao-Wei Deng,
Xiao-Jun Jia, Chang-De Xie, Kun-Chi Peng
Multipartite entangled state is the basic resource for implementing quantum information networks and quantum computation. In this paper, we present the experimental demonstration of the eightpartite two-diamond shape cluster states for continuous variables, which consist of eight spatially separated and entangled optical modes. Eight resource squeezed states of light with classical coherence are produced by four nondegenerate optical parametric amplifiers and then they are transformed to the eight-partite two-diamond shape cluster states by a specially designed linear optical network. Since the spatially separated multipartite entangled state can be prepared off-line, it can be conveniently applied in the future quantum technology.
Song-Song Li, Ji-Bing Yuan, Le-Man Kuang
We propose a scheme to coherently control spin squeezing of atomic Bose–Einstein condensate (BEC) via the technique of electromagnetically induced transparency (EIT). We study quantum dynamics of the mean spin vector and spin squeezing. It is shown that the mean spin vector and spin squeezing of the BEC can be controlled and manipulated by adjusting the external coupling fields or/and internal nonlinear interactions of the BEC. It is indicated that the spin squeezing can be generated rapidly in the dynamical process and maintained in a long time interval. It is found that a larger effective Rabi coupling between atoms and lasers can produce a stronger spin squeezing, and the squeezing can maintain a longer time interval.
Yun-Chen Wang, Cheng-Yin Wu, Yuan-Xing Liu, Shao-Hua Xu, Qi-Huang Gong
Strong fluorescence emissions were observed for nitrogen, carbon monoxide, and carbon dioxide molecules in intense femtosecond laser fields. These emissions can be assigned to the transitions of the molecular ions from the excited electronic states to the ground electronic states. The formation mechanisms were discussed and the lifetimes were measured for these excited molecular ions in intense laser fields.
Many nonlinear quantum optical physics phenomena need more accurate wave functions and corresponding energy or quasienergy levels to account for. An analytic expression of wave functions with
corresponding energy levels for an atomic electron interacting with a photon field is presented as an exact solution to the Schr¨odinger-like equation involved with both atomic Coulomb interaction and electron–photon interaction. The solution is a natural generalization of the quantum-field Volkov states for an otherwise free electron interacting with a photon field. The solution shows that an N level atom in light form stationary states without extra energy splitting in addition to the Floquet mechanism. The treatment developed here with computing codes can be conveniently transferred to quantum optics in classical-field version as research tools to benefit the whole physics community.
Yuan-Yuan Tang, Jian-Dong Guo
We present the temperature dependent electrical transport measurements of Ag/Si(111)-(√3 ×√3)R30◦ by the in situ micro-four-point probe method integrated with scanning tunneling microscopy. The surface structure characterizations show hexagonal patterns at room temperature, which supports the inequivalent triangle (IET) model. A metal–insulator transition occurs at ∼115 K.The lowtemperature transportmeasurements clearly reveal the strong localization characteristics of the insulating phase.
W. LiMing, Jia-Yun Luo, Xiao-Xue Cai, Ke Sha, Cheng-Ping Yin, Liang-Bin Hu
The tunneling spectrum of an electron and a hole in a superlattice of NS junctions is computed using
the BTK approach and the transfer matrix method. It shows sharp resonances at some energies above the superconducting gap. The sharper the resonance is the more layers the superlattice has. We find for the first time a mechanism to balance the incident and outgoing currents on the superlattice by averaging over the phase between the incident electron and the incident hole. This mechanism is more natural and physical than those in literatures.
Jie Meng, Jing Peng, Shuang-Quan Zhang, Peng-Wei Zhao
Magnetic rotation and antimagnetic rotation are exotic rotational phenomena observed in weakly deformed or near-spherical nuclei, which are respectively interpreted in terms of the shears mechanism and two shearslike mechanism. Since their observations, magnetic rotation and antimagnetic rotation phenomena have been mainly investigated in the framework of tilted axis cranking based on the pairing plus quadrupole model. For the last decades, the covariant density functional theory and its extension have been proved to be successful in describing series of nuclear ground-states and excited states properties, including the binding energies, radii, single-particle spectra, resonance states, halo phenomena, magnetic moments, magnetic rotation, low-lying excitations, shape phase transitions, collective rotation and vibrations, etc. This review will mainly focus on the tilted axis cranking covariant density functional theory and its application for the magnetic rotation and antimagnetic rotation phenomena.
Xiang-Dong Zhang, Yong-Ge Ma
A general nonperturvative loop quantization procedure for metric modified gravity is reviewed. As
an example, this procedure is applied to scalar-tensor theories of gravity. The quantum kinematical framework of these theories is rigorously constructed. Both the Hamiltonian and master constraint operators are well defined and proposed to represent quantum dynamics of scalar-tensor theories. As an application to models, we set up the basic structure of loop quantum Brans–Dicke cosmology. The effective dynamical equations of loop quantum Brans–Dicke cosmology are also obtained, which lay a foundation for the phenomenological investigation to possible quantum gravity effects in cosmology.
Bo Yan, Ai-Guo Xu, Guang-Cai Zhang, Yang-Jun Ying, Hua Li
In this paper we present a lattice Boltzmann model for combustion and detonation. In this model the
fluid behavior is described by a finite-difference lattice Boltzmann model by Gan et al. [Physica A, 2008, 387: 1721]. The chemical reaction is described by the Lee–Tarver model [Phys. Fluids, 1980, 23: 2362]. The reaction heat is naturally coupled with the flow behavior. Due to the separation of time scales in the chemical and thermodynamic processes, a key technique for a successful simulation is to use the operator-splitting scheme. The new model is verified and validated by well-known benchmark tests. As a specific application of the new model, we studied the simple steady detonation phenomenon. To show the merit of LB model over the traditional ones, we focus on the reaction zone to study the non-equilibrium effects. It is interesting to find that, at the von Neumann peak, the system is nearly in its thermodynamic equilibrium. At the two sides of the von Neumann peak, the system deviates from its equilibrium in opposite directions. In the front of von Neumann peak, due to the strong compression from the reaction product behind the von Neumann peak, the system experiences a sudden deviation from thermodynamic equilibrium. Behind the von Neumann peak, the release of chemical energy results in thermal expansion of the matter within the reaction zone, which drives the system to deviate the thermodynamic equilibrium in the opposite direction. From the deviation from thermodynamic equilibrium, Δ∗m, defined in this paper, one can understand more on the macroscopic effects of the system due to the deviation from its thermodynamic equilibrium.