|
Unitarity Schrödinger Equation and Ground State Properties of the Finite Trapped Superfluid Fermi Gases in a BCS-BEC Crossover
ZHANG Wen-Yuan, WANG Cheng-Tao, MA Yong-Li
Chin. Phys. Lett. 2010, 27 (4):
040304
.
DOI: 10.1088/0256-307X/27/4/040304
On the basis of quantum hydrodynamical equations we derive a unitarity Schrödinger equation of a finite trapped superfluid Fermi gas valid in the whole interaction regime from BCS superfluid to BEC. This equation is just the Ginzburg-Laudau-type equation for the fermionic Cooper pairs in the BCS side, the Gross-Pitaevskii-type equation for the bosonic dimers in the BEC side, and a unitarity equation for a strongly interacting Fermi superfluid in the unitarity limit. By taking a modified Gauss-like trial wave function, we solve the unitarity Schrödinger equation, calculate the energy, chemical potential, sizes and profiles of the ground-state condensate, and discuss the properties of the ground state in the entire BCS-BEC crossover regimes.
|
|
Preparation of Arbitrary Four-Qubit W State with Atomic Ensembles via Rydberg Blockade
HAN Yang, WU Chun-Wang, GAO Ming, LIANG Lin-Mei, CHEN Ping-Xing, LI Cheng-Zu
Chin. Phys. Lett. 2010, 27 (4):
040307
.
DOI: 10.1088/0256-307X/27/4/040307
The generation of various entangled states is an essential task in quantum information processing. Recently, a scheme (PRA 79, 022304) has been suggested for generating Greenberger-Horne-Zeilinger state and cluster state with atomic ensembles based on the Rydberg blockade. Using similar resources as the earlier scheme, here we propose an experimentally feasible scheme of preparing arbitrary four-qubit W class of maximally and non-maximally entangled states with atomic ensembles in a single step. Moreover, we carefully analyze the realistic noises and predict that four-qubit W states can be produced with high fidelity (F~0.994) via our scheme.
|
|
Determination of J/φ Event Number via J/φ→μ+μ- and J/φ→ e+e- at BESIII
LI Jiang, LIAO Xiao-Tao, YANG Ming, YANG Hong-Xun, XU Min, ZHANG Bing-Xin, SHEN Xiao-Yan, YANG Yong-Xu
Chin. Phys. Lett. 2010, 27 (4):
041301
.
DOI: 10.1088/0256-307X/27/4/041301
The decays of J/φ→μ+μ- and J/φ→ e+e- are studied by Monte-Carlo simulation, based on the Beijing Spectrometer (BES)Ⅲ offline software system. The methods of determination of the J/φ event number via J/φ→μ+μ- and J/φ→ e+e- are presented, respectively. These methods can be used to determine the J/φevent number for the coming BESⅢ J/φ data sample.
|
|
Proton Ratio of HL-2A Bucket Ion Source
YU Li-Ming, LEI Guang-Jiu, CAO Jian-Yong, YANG Li-Mei, JIANG Shao-Feng, HAN Xiao-Yu, ZHANG Xian-Ming, SUN Ping, ZOU Gui-Qing, LU Da-Lun, LIU He, JIANG Tao, DUAN Xu-Ru
Chin. Phys. Lett. 2010, 27 (4):
042901
.
DOI: 10.1088/0256-307X/27/4/042901
For heating the tokamak plasma effectively, the ion source must be capable of producing ions with high proton ratio. The proton ratio, which is found to be more than 65.6% at the ion current of 19.6 A with the extraction voltage of 39.6 kV, is measured with an image spectrograph by Doppler shift effect of Balmer-α-radiation spectrum emitted from fast hydrogen particles. The tendency of proton ratio with the ion density in experiment is almost the same as the mode devised by Zhang et al. Okumura et al. only gave the affection of the plasma volume and ion loss area on the proton ratio, but the relationship between the ion density in chamber and the proton ratio was not presented. We give the relationship.
|
|
Rotational and Vibrational State Distributions of CsH and Relative Reactivity in Reactions of Cs(62D,72D) with H2
WANG Da-Gui, WANG Xue-Yan, ZHOU Dong-Dong, MU Li-Sai, SHEN Yi-Fan, DAI Kang
Chin. Phys. Lett. 2010, 27 (4):
043402
.
DOI: 10.1088/0256-307X/27/4/043402
By using a pump-probe technique, the nascent rotational and vibrational state distributions of CsH are obtained in the Cs(62D,72D) plus H2 reaction. The nascent CsH molecules are found to populate the lowest two vibrational (v”=0 and 1) levels of the ground electronic state. By comparing the spectral intensities of the CsH action spectra with those of pertinent Cs atomic fluorescence excitation spectra, the relative reactivity with H2 is in an order of 62D3/2>62D5/2>72D3/2>72D5/2. The rotational temperatures are found to be slightly below the cell temperature. The relative fractions (< 402;V>, <402;R>, <402;T>) of average energy disposal are derived as (0.2,0.12,0.68), (0.2,0.12,0.68), (0.07,0.04,0.89) and (0.07,0.04,0.89) for the 62D3/2, 62D5/2,72D3/2 and 72D5/2, respectively. The major available energy is released as translation. These results support that the reaction mechanism of Cs( 62D,72D) plus H2 is primarily a collinear abstraction and not an insertion.
|
|
An Experimental Observation of Axial Variation of Average Size of Methane Clusters in a Gas Jet
HAN Ji-Feng, YANG Chao-Wen, MIAO Jing-Wei, LU Jian-Feng, LIU Meng, LUO Xiao-Bing, SHI Mian-Gong
Chin. Phys. Lett. 2010, 27 (4):
043601
.
DOI: 10.1088/0256-307X/27/4/043601
Axial variation of average size of methane clusters in a gas jet produced by supersonic expansion of methane through a cylindrical nozzle of 0.8 mm in diameter is observed using a Rayleigh scattering method. The scattered light intensity exhibits a power scaling on the backing pressure ranging from 16 to 50 bar, and the power is strongly Z dependent varying from 8.4 (Z=3 mm) to 5.4 (Z=11 mm), which is much larger than that of the argon cluster. The scattered light intensity versus axial position shows that the position of 5 mm has the maximum signal intensity. The estimation of the average cluster size on axial position Z indicates that the cluster growth process goes forward until the maximum average cluster size is reached at $Z=9$ mm, and the average cluster size will decrease gradually for Z>9 mm.
|
|
High Power THz Undulator Radiation from Linear Accelerator
LIN Xu-Ling, ZHANG Jian-Bing, LU Yu, LUO Feng, LU Shan-Liang, YU Tie-Min, DAI Zhi-Min,
Chin. Phys. Lett. 2010, 27 (4):
044101
.
DOI: 10.1088/0256-307X/27/4/044101
A 30-MeV femto-second electron linac is built at the Shanghai Institute of Applied Physics, which can produce high power, coherent THz undulator radiation. We report the experimental facility and measurement of the power, frequency spectrum. First experiments show the averaged power at THz to be about 20 mW.
|
|
Laser-Induced Silver Nanoparticles Deposited on Optical Fiber Core for Surface-Enhanced Raman Scattering
LI Ming-Shan, YANG Chang-Xi
Chin. Phys. Lett. 2010, 27 (4):
044202
.
DOI: 10.1088/0256-307X/27/4/044202
We report on surface-enhanced Raman scattering (SERS) probes based on silver nanoparticles which are deposited on the core of the distal end of standard single mode fibers, by means of the very simple, versatile, and low-cost laser-induced nanoparticle technique. The morphological features of the Ag nanoparticles vary according to the experimental conditions such as laser power, illumination time, and concentration of the reaction solution. The SERS activity of the probes is demonstrated with the detections of rhodamine 6G aqueous solutions. The detections are made from both ends of the probes, i.e., in direct detection mode from the end with nanoparticles and in remote detection mode from the distal end, respectively.
|
|
Growth of Pure Zinc Blende GaAs Nanowires: Effect of Size and Density of Au Nanoparticles
YE Xian, HUANG Hui, REN Xiao-Min, YANG Yi-Su, GUO Jing-Wei, HUANG Yong-Qing, WANG Qi
Chin. Phys. Lett. 2010, 27 (4):
046101
.
DOI: 10.1088/0256-307X/27/4/046101
Pure zinc blende GaAs nanowires were grown by metal organic chemical vapor deposition on GaAs(111)B substrates via Au catalyzed vapor-liquid-solid mechanism. The diameter, size distribution, and density of Au particles can be changed by varying the Au film thickness. We find that the grown nanowires are of rod-like shapes and pure zinc blende structure; moreover, the growth rate depends on the density of Au particles and it is independent of its diameters. It can be concluded that the nanowire was grown with main contributions from the direct impingement of vapor species onto the Au-Ga droplets and contributions from adatom diffusion can be negligible. The results indicate that the droplet acts as a catalyst rather than an adatom collector.
|
|
Raman Spectrum of Epitaxial Graphene on SiC (0001) by Pulsed Electron Irradiation
HUANG Qing-Song, GUO Li-Wei, WANG Wen-Jun, WANG Gang, WANG Wan-Yan, JIA Yu-Ping, LIN Jing -Jing, LI Kang, CHEN Xiao-Long
Chin. Phys. Lett. 2010, 27 (4):
046803
.
DOI: 10.1088/0256-307X/27/4/046803
We report new Raman features of epitaxial graphene (EG) on Si-face 4H-SiC prepared by pulsed electron irradiation (PEI). With increasing graphene layers, frequencies of G and 2D peaks show blue-shifts and approach those of bulk highly-oriented pyrolytic graphite. It is indicated that the EG is slightly tension strained and tends to be strain-free. Meanwhile, single Lorentzian line shapes are well fitted to the 2D peaks of EG on SiC(0001) and their full widths at half maximum decrease with the increasing graphene layers, which indicates that the multilayer EG on Si-face can also contain turbostratic stacking by our PEI route instead of only AB Bernal stacking by a traditional thermal annealing method. It is worth noting that the stacking style plays an important role on the charge carrier mobility. Therefore our findings will be a candidate for growing quality graphene with high carrier mobility both on the Si- and C-terminated SiC substrate. Mechanisms behind the features are studied and discussed.
|
|
Long-Lasting Phosphorescence Properties of Pyrochlore La2Ti2O7:Pr3+ Phosphor
CHU Ming-Hui, JIANG Da-Peng, ZHAO Cheng-Jiu, LI Bin
Chin. Phys. Lett. 2010, 27 (4):
047203
.
DOI: 10.1088/0256-307X/27/4/047203
The La2Ti2O7:Pr3+, which emits red color luminescence upon UV light excitation, is prepared by the conventional high-temperature solid-state method and its luminescent properties are systematically investigated. X-ray diffraction, photoluminescence, afterglow emission spectra and long-lasting phosphorescence (LLP) decay curves are used to characterize this phosphor. After irradiation by a 290-nm UV light for 3 min, the Pr3+-doped La2Ti2O7 phosphor emits intense red emitting afterglow from the 1D2→3H4 transitions, and its afterglow can be seen with the naked eye in the dark clearly for more than 1 h after removal of the excitation source. The afterglow decay curve of the Pr3+-doped La2Ti2O7 phosphor contains a fast decay component and another slow decay one. The possible mechanism of this red light emitting LLP phosphor is also discussed based on the experimental results.
|
|
Fabrication and Properties of Double-Side Tl2Ba2CaCu2O8 Thin Film on CeO2 Buffered Sapphire Substrate
YOU Feng, WANG Zheng, XIE Qing-Lian, JI Lu, YUE Hong-Wei, ZHAO Xin-Jie, FANG Lan, YAN Shao-Lin
Chin. Phys. Lett. 2010, 27 (4):
047401
.
DOI: 10.1088/0256-307X/27/4/047401
The double-side Tl2Ba2CaCu2O8 (Tl-2212) superconducting thin films were fabricated on CeO2 buffered sapphire substrates. The reactive magnetron sputtering technique was used to grow CeO2 buffer thin films on sapphire substrates. Making use of the metal cerium as a sputtering source, the depositing rate is much higher compared with the CeO2 target. The Tl-2212 thin films on CeO2 buffered sapphire substrates were fabricated by a dc magnetron sputtering and post-annealing process. The x-ray diffraction indicates that the thin film is pure Tl-2212 phase with the c-axis perpendicular to the substrate surfaces, and epitaxially grown on the CeO2 buffered sapphire. The critical transition temperature Tc is around 106 K, the critical current density Jc is around 3.5 MA/cm2 at 77 K, and the microwave surface resistance Rs at 77 K and 10 GHz of the film is as low as 390 μΩ
|
|
Mechanical Reinforcement and Piezoelectric Properties of PZT Ceramics Embedded with Nano-Crystalline
WANG Da-Wei, , JIN Hai-Bo, , YUAN Jie, WEN Bao-Li ZHAO Quan-Liang, ZHANG De-Qing, CAO Mao-Sheng
Chin. Phys. Lett. 2010, 27 (4):
047701
.
DOI: 10.1088/0256-307X/27/4/047701
The double-scale lead zirconate titanate (PZT) piezoelectric ceramics were prepared by the solid state processing with PZT nano-crystalline and micro-powder. The microstructures, electrical and mechanical properties of the double-scale PZT are investigated. All the sintered ceramics exhibit a single perovskite structure and the grain size of the double-scale PZT reduces due to the incorporation of PZT nano-crystalline. Compared to normal PZT, the mechanical properties increase significantly and the piezoelectric properties decrease slightly. Mechanisms responsible for the reinforcement of the double-scale PZT are discussed.
|
|
A Photovoltaic InAs Quantum-Dot Infrared Photodetector
TANG Guang-Hua, XU Bo, JIANG Li-Wen, KONG Jin-Xia, KONG Ning, LIANG De-Chun, LIANG Ping, YE Xiao-Ling, JIN Peng, LIU Feng-Qi, CHEN Yong-Hai, WANG Zhan-Guo
Chin. Phys. Lett. 2010, 27 (4):
047801
.
DOI: 10.1088/0256-307X/27/4/047801
A photovoltaic quantum dot infrared photodetector with InAs/GaAs/AlGaAs structures is reported. The detector is sensitive to normal incident light. At zero bias and 78 K, a clear spectral response in the range of 2-7 μm has been obtained with peaks at 3.1, 4.8 and 5.7 μm. The bandgap energies of GaAs and Al0.2Ga0.8As at 78 K are calculated and the energy diagram of the transitions in the Quantum-Dot Infrared Photodetector (QDIP) is given out. The photocurrent signals can be detected up to 110 K, which is state-of-the-art for photovoltaic QDIP. The photovoltaic effect in our detector is a result of the enhanced band asymmetry as we design in the structure.
|
|
Growth and Characteristics of Freestanding Hemispherical Diamond Films by Microwave Plasma Chemical Vapor Deposition
WANG Qi-Liang, LÜ, Xian-Yi, LI Liu-An, CHENG Shao-Heng, LI Hong-Dong
Chin. Phys. Lett. 2010, 27 (4):
047802
.
DOI: 10.1088/0256-307X/27/4/047802
Freestanding hemispherical diamond films have been fabricated by microwave plasma chemical vapor deposition using graphite and molybdenum (Mo) as substrates. Characterized by Raman spectroscopy and scanning electron microscopy, the crystalline quality of the films deposited on Mo is higher than that on graphite, which is attributed to the difference in intrinsic properties of the two substrates. By decreasing the methane concentration, the diamond films grown on the Mo substrate vary from black to white, and the optical transparency is enhanced. After polishing the growth side, the diamond films show an infrared transmittance of 35-60% in the range 400-4000 cm-1.
|
|
Effects of Annealing Temperature on Structural and Optical Properties of ZnO Thin Films
XU Jian-Ping, SHI Shao-Bo, LI Lan, ZHANG Xiao-Song, WANG Ya-Xin, CHEN Xi-Ming
Chin. Phys. Lett. 2010, 27 (4):
047803
.
DOI: 10.1088/0256-307X/27/4/047803
The effects of annealing temperature on the structural and optical properties of ZnO films grown on Si (100) substrates by sol-gel spin-coating are investigated. The structural and optical properties are characterized by x-ray diffraction, scanning electron microscopy and photoluminescence spectra. X-ray diffraction analysis shows the crystal quality of ZnO films becomes better after annealing at high temperature. The grain size increases with the temperature increasing. It is found that the tensile stress in the plane of ZnO films first increases and then decreases with the annealing temperature increasing, reaching the maximum value of 1.8 GPa at 700 \circC. PL spectra of ZnO films annealed at various temperatures consists of a near band edge emission around 380 nm and visible emissions due to the electronic defects, which are related to deep level emissions, such as oxide antisite (OZn), interstitial oxygen (Oi), interstitial zinc (Zni) and zinc vacancy,which are generated during annealing process. The evolution of defects is analyzed by PL spectra based on the energy of the electronic transitions.
|
|
Electrical Studies on Pentacene Thin Film Transistors with Different Channel Widths
Jaya Lohani, Manoj Gaur, Upendra Kumar, V. R. Balakrishnan, Harsh, S. V. Eswaran
Chin. Phys. Lett. 2010, 27 (4):
048102
.
DOI: 10.1088/0256-307X/27/4/048102
In order to conduct electrical studies on organic thin film transistors, top-contact devices are fabricated by growing polycrystalline films of freshly synthesized pentacene over Si/SiO2 substrates with two different channel widths under identical conditions. Reasonable field effect mobilities in order of 10-2-10-3 cm2V-1s-1 are obtained in these devices. An elaborative electrical characterization of all the devices is undertaken to study the variance in output saturation current, field effect mobility, and leakage current with aging under ambient conditions. As compared to the devices with longer channel width, the devices with shorter channel width exhibit better electrical performance initially. However, the former devices sustain the moderate performance much longer than the latter ones.
|
|
A Low-Voltage Silicon Light Emitting Device in Standard Salicide CMOS Technology
WANG Wei, HUANG Bei-Ju, DONG Zan, LIU Hai-Jun, ZHANG Xu, GUAN Ning, CHEN Jin, GUO Wei-Lian, NIU Ping-Juan, CHEN Hong-Da
Chin. Phys. Lett. 2010, 27 (4):
048501
.
DOI: 10.1088/0256-307X/27/4/048501
A silicon-based field emission light emitting diode for low-voltage operation is fabricated in the standard 0.35 μm 2P4M salicide complementary metal-oxide-semiconductor (CMOS) technology. Partially overlapping p+ and n+ regions with a salicide block layer are employed in this device to constitute a heavily doped p+-n+ junction which has soft "knee" Zener breakdown characteristics, thus its working voltage can be reduced preferably below 5 V, and at the same time the power efficiency is improved. The spectra of this device are spread over 500 nm to 1000 nm with the main peak at about 722 nm and an obvious red shift of the spectra peak is observed with the increasing current through the device. During the emission process, field emission rather than avalanche process plays a major role. Differences between low-voltage Zener breakdown emission and high-voltage avalanche breakdown emission performance are observed and compared.
|
|
Interest-Driven Model for Human Dynamics
SHANG Ming-Sheng, CHEN Guan-Xiong, DAI Shuang-Xing, WANG Bing-Hong, ZHOU Tao,
Chin. Phys. Lett. 2010, 27 (4):
048701
.
DOI: 10.1088/0256-307X/27/4/048701
Empirical observations indicate that the interevent time distribution of human actions exhibits heavy-tailed features. The queuing model based on task priorities is to some extent successful in explaining the origin of such heavy tails, however, it cannot explain all the temporal statistics of human behavior especially for the daily entertainments. We propose an interest-driven model, which can reproduce the power-law distribution of interevent time. The exponent can be analytically obtained and is in good accordance with the simulations. This model well explains the observed relationship between activities and power-law exponents, as reported recently for web-based behavior and the instant message communications.
|
69 articles
|