The amplitudes of different pairing gap components induced by J1, J2 with J2'=0 at electron doping =0.51.sNNN is the s wave resulting from NNN AFM coupling, sx2+y2 and dx2-y2 from NN AFM coupling.The pairing strength of sNNN is peaked around the doping level x = 0.5, which is consistent with experimental observation. >sNNN is also very robust against spin-orbital coupling. Moreover, it can be distinguished from conventional s-wave pairing by measuring and comparing superconducting gaps of different Fermi surfaces. For more details, please refer to the article “Pairing symmetry in layered BiS2 compounds driven by electron–electron correlation” by Yi Liang et al., pp 194–199. [Photo credits: Yi Liang, Institute of Physics, Chinese Academy of Sciences] [Detail] ...
We review our theoretical advances in quantum tunneling of Bose–Einstein condensates in optical traps and in microcavities. By employing a real physical system, the frequencies of the pseudo Goldstone modes in different phases between two optical traps are studied respectively, which are the crucial feature of the non-Abelian Josephson effect. When the optical lattices are under gravity, we investigate the quantum tunneling in the “Wannier–Stark localization” regime and “Landau–Zener tunneling” regime. We finally get the total decay rate and the rate is valid over the entire range of temperatures. At high temperatures, we show how the decay rate reduces to the appropriate results for the classical thermal activation. At intermediate temperatures, the results of the total decay rate are consistent with the thermally assisted tunneling. At low temperatures, we obtain the pure quantum tunneling ultimately. And we study the alternating-current and direct-current (ac and dc) photonic Josephson effects in two weakly linked microcavities containing ultracold two-level atoms, which allows for direct observation of the effects. This enables new investigations of the effect of many-body physics in strongly coupled atom-cavity systems and provides a strategy for constructing novel interference devices of coherent photons. In addition, we propose the experimental protocols to observe these quantum tunneling of Bose–Einstein condensates.
We experimentally study the phase regulated switch between electromagnetically induced transparency and electromagnetically induced absorption in probe transmission signal and the conversion between enhancement and suppression in four-wave mixing and fluorescence signals for the first time. By changing the relative phase, electromagnetically induced transparency can be converted into electromagnetically induced absorption. In this process, the conversion from suppression to enhancement is also obtained in four-wave mixing and fluorescence signals. This research can be applied in non-linear optical device like optical switch and optical wavelength convertor.
By solving the quantum Vlasov equation, electron–positron pair production in a strong electric field with asymmetric laser pulses has been investigated. We consider three different situations of subcycle, cycle and supercycle laser pulses. It is found that in asymmetric laser pulse field, i.e., when the pulse length of one rising or falling side is fixed while the pulse length of the other side is changed, the pair production rate and number density can be significantly modified comparable to symmetric situation. For each case of these three different cycle pulses, when one side pulse length is constant and the other side pulse length becomes shorter, i.e., the whole pulse is compressed, the more pairs can be produced than that in the vice versa case, i.e., the whole pulse is elongated. In compressed pulse case there exists an optimum pulse length ratio of asymmetric pulse lengths which makes the pair number density maximum. Moreover, the created maximum pair number density by subcycle pulse is larger than that by cycle or/and supercycle pulse. In elongated pulse case, however, only for supercycle laser pulse the created pairs is enhanced and there exists also an optimum asymmetric pulse length ratio that maximizes the pair number density. On the other hand, surprisingly, in both cases of subcycle and cycle elongated laser pulses, the pair number density is monotonically decreasing as the asymmetry of pulse increases.
Based on the scattering matrix approach, we systematically investigate the anharmonic effect of the pumped current in double-barrier structures with adiabatic time-modulation of two sinusoidal AC driven potential heights. The pumped current as a function of the phase difference between the two driven potentials looks like to be sinusoidal, but actually it contains sine functions of double and more phase difference. It is found that this kind of anharmonic effect of the pumped current is determined combinedly by the Berry curvature and parameter variation loop trajectory. Therefore small ratio of the driving amplitude and the static amplitude is not necessary for harmonic pattern in the pumped current to dominate for smooth Berry curvature on the surface within the parametervariation loop.
In this contribution, we briefly recall the basic concepts of quantum optics and properties of semiconductor quantum dot (QD) which are necessary to the understanding of the physics of single-photon generation with single QDs. Firstly, we address the theory of quantum emitter-cavity system, the fluorescence and optical properties of semiconductor QDs, and the photon statistics as well as optical properties of the QDs. We then review the localization of single semiconductor QDs in quantum confined optical microcavity systems to achieve their overall optical properties and performances in terms of strong coupling regime, efficiency, directionality, and polarization control. Furthermore, we will discuss the recent progress on the fabrication of single photon sources, and various approaches for embedding single QDs into microcavities or photonic crystal nanocavities and show how to extend the wavelength range. We focus in particular on new generations of electrically driven QD single photon source leading to high repetition rates, strong coupling regime, and high collection efficiencies at elevated temperature operation. Besides, new developments of room temperature single photon emission in the strong coupling regime are reviewed. The generation of indistinguishable photons and remaining challenges for practical single-photon sources are also discussed.
We investigate the pairing symmetry of layered BiS2 compounds by assuming that electron-electron correlation is still important so that the pairing is rather short range. We find that the extended
The geometries, formation energies and electronic band structures of (8, 0) and (14, 0) single-walled carbon nanotubes (SWCNTs) with various defects, including vacancy, Stone–Wales defect, and octagon–pentagon pair defect, have been investigated within the framework of the density-functional theory (DFT), and the influence of the concentration within the same style of defect on the physical and chemical properties of SWCNTs is also studied. The results suggest that the existence of vacancy and octagon–pentagon pair defect both reduce the band gap, whereas the SW-defect induces a band gap opening in CNTs. More interestingly, the band gaps of (8, 0) and (14, 0) SWCNTs configurations with two octagon–pentagon pair defect presents 0.517 eV and 0.163 eV, which are a little smaller than the perfect CNTs. Furthermore, with the concentration of defects increasing, there is a decreasing of band gap making the two types of SWCNTs change from a semiconductor to a metallic conductor.
The structure, electronic and magnetic properties of HoSi
The physical properties of Zr
A two-dimensional electromagnetic Particle-in-Cell (PIC) simulation model is proposed to study the propagation of intense ion beams with beam width
Based on a theory of extra dimensional confinement of quantum particles [E. R. Hedin, Physics Essays, 2012, 25(2): 177], a simple model of a nucleon–nucleon (NN) central potential is derived which quantitatively reproduces the radial profile of other models, without adjusting any free parameters. It is postulated that a higher-dimensional simple harmonic oscillator confining potential localizes particles into three-dimensional (3D) space, but allows for an evanescent penetration of the particles into two higher spatial dimensions. Producing an effect identical with the relativistic quantum phenomenon of
In this article, we present a new type of unified dynamic scaling property for synchronizability, which can describe the scaling relationship between dynamic synchronizability and four hybrid ratios under the unified hybrid network theory framework (UHNTF). Our theory results can not only be applied to judge and analyze dynamic synchronizability for most of complex networks associated with the UHNTF, but also we can flexibly adjust and design different hybrid ratios and scaling exponent to meet actual requirement for the dynamic characteristics of the UHNTF.
In the paper we extend the Multiple-Relaxation-Time (MRT) Lattice Boltzmann (LB) model proposed in [