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Entanglement of Two-Qubit Quantum Heisenberg XYZ Chain
XI Xiao-Qiang, HAO San-Ru, CHEN Wen-Xue, YUE Rui-Hong
Chin. Phys. Lett. 2002, 19 (8):
1044-1047
.
We derive the analytic expression of the concurrence in the quantum Heisenberg XYZ model and discuss the influence of parameters J, Δ, and Γ on the concurrence. By choosing different values Γ and Δ, we obtain the XX, XY, XXX and XXZ chains. The concurrence decreases with increasing temperature. When T → 0, the concurrence reaches its maximum value 1, i.e., the entangled state, | > = √2/2 (|01> - |10>), is maximum entanglement. For the XXZ chain, when Γ → ∞, the concurrence will meet its maximum value Cmax = sinh(1/T)/cosh(1/T).
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Halo Structure of Isobaric Analog States in A = 21 and 17 Mirror Nuclei
ZHOU Shu-Hua, ZHOU Jing
Chin. Phys. Lett. 2002, 19 (8):
1065-1067
.
The root-mean-square (rms) radius of the last nucleon in the 2s1/2 state of 21Ne, 21Na, 17O, and 17F are found to be 4.4±0.5, 5.2±0.6, 4.3±0.5, and 5.0±0.6 fm, respectively, from transfer reaction data. The results show that the 2s1/2 states of 21Na and 17F are proton halo states, while the analogous states in their mirror nuclei 21Ne and 17O can be considered as neutron skin states. Comparisons among the rms radii of these states lead us to expect that a neutron halo nucleus has a proton halo mirror partner, and the Coulomb barrier is a determinant factor limiting the extension of the rms radius of the loosely bound proton.
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One-Proton Halo in 31Cl with Relativistic Mean-Field
Theory
CAI Xiang-Zhou, SHEN Wen-Qing, , REN Zhong-Zhou, JIANG Wei-Zhou, FANG De-Qing, ZHANG Hu-Yong, ZHONG Chen, WEI Yi-Bin, GUO Wei,
MA Yu-Gang, ZHU Zhi-Yuan
Chin. Phys. Lett. 2002, 19 (8):
1068-1070
.
We investigate proton-rich isotopes 31,32Cl using the nonlinear relativistic mean-field model. It is shown that this model can reproduce the properties of these nuclei well. A long tail appears in the calculated proton density distribution of 31Cl. The results of relativistic density-dependent Hartree theory show a similar trend of tail density distribution. It is strongly suggested that there is a proton halo in 31Cl and it is indicated that there may exist proton skin in 31Cl. The relation between the proton halo in 1Cl and the new proton magic number is discussed.
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Halo Nature of 14,15C
LIU Zu-Hua
Chin. Phys. Lett. 2002, 19 (8):
1071-1073
.
We have used spectroscopic factors extracted from the (d,p) transfer reactions to calculate asymptotic normalization coefficients and root-mean-square (rms) radii for the valence neutron in 14,15C. The obtained rms radii are 4.57±0.30, 5.78±0.36 and 5.82±0.60 fm for the first 1-, 0- excited states of 14C and the ground state of 15C, which are 1.84, 2.33 and 2.32 times larger than the size of their cores, repectively. These large values imply that 15C as well as 14C in its first 1-, 0- states are halo nuclei.
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Experimental Test of the Non-reproducibility of Cross
Sections in Dissipative Reactions
DONG Yu-Chuan, WANG Qi, TIAN Wen-Dong, LI Song-Lin, LI Zhi-Chang, LU Xiu-Qin, ZHAO Kui, FU Chang-Bo, LIU Jian-Cheng, JIANG Hua, HU Gui-Qing
Chin. Phys. Lett. 2002, 19 (8):
1074-1077
.
Two independent measurements of cross sections for the 19F+93Nb dissipative heavy ion collisions have been performed at incident energies from 100 to 108 MeV in a step of 250 keV. In the two measurements, two independently prepared targets were used. All other experimental conditions were identical in both experiments. The data indicate that non-reproducibility of the non-self-averaging oscillation is yielded in the two measurements. This supports the recent theoretical predictions of spontaneous coherence, slow phase randomization and extreme sensitivity in highly excited complex quantum systems.
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Yb3+-Doped Non-π-Phase-Shifted Distributed Feedback
Fibre Lasers
FAN Wei, CHEN Bai, LI Xue-Chun, CHEN Lan-Rong, CHEN Shao-He, LIN Zun-Qi
Chin. Phys. Lett. 2002, 19 (8):
1108-1111
.
Distributed feedback (DFB) fibre lasers usually have two longitudinal modes symmetrically located at each side of the Bragg wavelength because they have the same lowest gain threshold. In order to obtain single longitudinal output, π-phase-shift, DFB fibre lasers were often adopted. However, we found that, even with no π-phase-shift, the single frequency output can be acquired from Yb3+-doped fibre DFB lasers. The polarization beat frequency was measured to be 366 MHz.
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Monopole Charge Domain in High-Gain Gallium Arsenide Photoconductive Switches
SHI Wei, CHEN Er-Zhu, ZHANG Xian-Bin, LI Qi
Chin. Phys. Lett. 2002, 19 (8):
1119-1121
.
Considering that the semi-insulating gallium arsenide photoconductive switches can be triggered into the high gain mode and no reliable theories can account for the observed transient characteristics, we propose the monopole charge domain model to explain the peculiar switching phenomena occurring in the high gain mode and discuss the requirements for the lock-on switching. During operation on this mode, the applied field across the switch and the lock-on field are all larger than the Guun threshold field. Our developed monopole charge domain is based on the transferred-electron effect, but the domain is only composed of large numbers of electrons piled up due to the negative differential mobility. Using the model and taking the physical mechanism of the avalanche impact ionization and recombination radiation into consideration, we interpret the typical phenomena of lock-on effect, such as, delay time between the beginning of optical illumination and turning-on of the switch, conduction mechanism of the sustaining phase. Under different conditions of bias field intensity and incident light energy, the delay time of the switching are calculated. The results show that the physical mechanism of impact ionization and recombination radiation occurring in the monopole charge domain is responsible for the lock-on switching.
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Optical Properties of ZnCdSe/ZnMgSe Multiple Quantum Wells Grown by Molecular Beam Epitaxy
LÜ, You-Ming, SHEN De-Zhen, LIU Yi-Chun, LI Bing-Hui, LIANG Hong-Wei, ZHANG Ji-Ying, FAN Xi-Wu
Chin. Phys. Lett. 2002, 19 (8):
1152-1154
.
OWe study the optical properties of ZnCdSe/ZnMgSe multiple quantum wells using photoluminescence (PL) and Raman scattering spectra. In the PL spectra, an intense emission band coming from free exciton luminescence of the quantum wells can be observed from 80 K to 300 K. The exciton binding energy is evaluated by the dependence of PL intensity on the temperature, showing the behaviour of the better two-dimensional excitons. The result indicates that the enhancement of the confinement effect is due to containing Mg in the barrier layers. At room temperature, Raman scattering spectra are classified into the confined optical modes and folded optical modes. This confirms the formation of a multilayer system with a higher crystalline quality.
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Influences of Thalliation on the Morphology and Critical Temperature of Tl2Ba2CaCu2O8 Thin Films
LEI Chong, ZHAO Xin-Jie, WANG Tian-Sheng, PENG Wei, YU Hong-Chun, CHEN Ying-Fei, TIAN Yong-Jun, LI Lin
Chin. Phys. Lett. 2002, 19 (8):
1158-1160
.
Tl2Ba2CaCu2Ox (Tl-2212) thin films were prepared by the two-step technique. A precursor film was first prepared by the pulsed laser deposition method, and then experienced the incorporation of thalliation in a one-step or two-step annealing process. The experimental results show that the two-step annealing process produces dense and smooth films, and that the one-step annealing process produced a high critical temperature film of 101K, but the transition width is wide. Precursor films with homogeneous Ba2Ca1.3Cu2.1Ox composition are essential for producing high quality Tl-2212 films.
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Electrical Transport and Low-Field Magnetoresistance in La2/3Ca1/3MnO3/YSZ Composites
YUAN Song-Liu, XIA Zheng-Cai, LIU Sheng, LI Zhong-Yi, PENG Gang, TANG Jie, ZHANG Guo-Hong, ZHANG Li-Jiang, FENG Wen, XIONG Cao-Shui
Chin. Phys. Lett. 2002, 19 (8):
1168-1171
.
Electrical transport and low-field magnetoresistance (MR) are
reported for (1-x)LCMO/xYSZ composites (0 < x < 80%)(LCMO = La2/3Ca1/3MnO2 and YSZ being yttria stabilized zirconia). Different transport and MR behaviour are observed for x < 2% and x > 2%. In particular, the composite with x ≤ 1% shows a wide temperature window with a large constant MR below the transition. Based on the microscopy analysis, a possible interpretation is presented for different observations for x < 2% and x > 2% with emphasis on the boundary effect arising from insulating YSZ layers.
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Polarization-Induced Charges in Modulation-Doped AlxGa1-xN/GaN Heterostructures Through Capacitance-Voltage Profiling
ZHOU Yu-Gang, SHEN Bo, YU Hui-Qiang, LIU Jie, ZHOU Hui-Mei, ZHANG Rong, SHI Yi, ZHENG You-Dou, T. Someya, Y. Arakawa
Chin. Phys. Lett. 2002, 19 (8):
1172-1175
.
Polarization-induced charges in modulation-doped Al0.22Ga0.78N/GaN heterostructures were investigated by the capacitance-voltage (C--V) method. The C--V profile of the Pt/Al0.22Ga0.78N/GaN Schottky diodes with various Al0.22Ga0.78N thickness shows significant differences due to change of the polarization field in the heterostructures. Numerical simulation based on the experimental results indicates that the sheet density of the polarization-induced charges at the heterointerface is 6.78 x 1012cm-2 in the samples with the Al0.22Ga0.78N thickness of 30 nm or 45 nm. The charge density reduces to 1.30 x 1012cm-2 in the sample with the Al0.22Ga0.78N thickness of 75 nm. It is thought that the reduction of the polarization-induced charges at the heterointerface is due to the partial relaxation of the Al0.22Ga0.78N layer on GaN. This work provides a technique for quantitative characterization of the polarization-induced charges in AlxGa1-xN/GaN heterostructures.
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Effect of Substrates on CuInSe2 Nanoparticle Thin Films by Radio Frequency Reactive Sputtering
HUANG Shi-Yong, ZHANG Li-De, LI Guang-Hai, DAI Zhen-Hong, ZHU Xiao-Guang, QU Feng-Qi, FU Sheng-Qi, ZHONG Yu-Rong, MIAO Y
Chin. Phys. Lett. 2002, 19 (8):
1199-1202
.
CuInSe2 (CIS) nanoparticle thin films have been prepared by rf reactive magnetron sputtering from compound ternary fan-shaped targets on low temperature substrates with pure argon gas as the atmosphere. The stoichiometry of the ternary compound semiconductor quantum dots can be easily controlled by the ratios of the ternary elements and sputtering parameters. CIS nanoparticle thin films regularly shaped and distributed reasonably uniform in size on substrates of 7059 glass etc can be grown in this way. The average particle diameter can be varied between 40 and 80 nm by appropriate choice of the substrate temperature, power density and total CIS coverage. The optical and electrical properties of the CIS films have also been studied.
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56 articles
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