摘要：
The temperature and magnetic field dependence of the resistance of polycrystalline sample (La0.9Bi0.1)2/3Ca1/3MnO3 was investigated in pulsed high magnetic field up to 40T over a wide temperature region. In order to describe the magnetotransport properties of the sample, an extended Mott hopping conduction model was employed. Instead of B
J
(gμ
B
J(T)B/k
B
T) in the ferromagnetic (FM) state and
$B_{J}^{2}(g\mu_{B}J(T)B/k_{B}T)$
in the paramagnetic (PM) state, the magnetic field dependence of the resistance could scale nicely with the Brillouin function B
J
(gμ
B
J(T)B/k
B
T) in all the given temperatures (above and below the Curie temperatureT
c
). The deduced value of the average spin moment J(T) increases with the increasing of the temperature and reaches the maximum value (∼35) aroundT
c
. The large value of J(T) indicate the presence of magnetic clusters in the sample which is induced by the short-range ferromagnetic ordering, however, compared to the un-doped compound La2/3Ca1/3MnO3, the value of J(T) is much smaller, which might be ascribe to the location of the 6s2 lone pair electrons of Bi3+ ions in the sample (La0.9Bi0.1)2/3Ca1/3MnO3.
摘要：
Based on a single atom coupled to a fiber-coupled, chip-based microresonator [B. Dayan et al., Science 319, 1062 (2008)], we put forward a scheme to generate optical frequency combs at driving laser powers as low as a few nanowatts. Using state-of-the-art experimental parameters, we investigate in detail the influences of different atomic positions and taper-resonator coupling regimes on optical-frequency-comb generation. In addition to numerical simulations demonstrating this effect, a physical explanation of the underlying mechanism is presented. We find that the combination of the atom and the resonator can induce a large third-order nonlinearity which is significantly stronger than Kerr nonlinearity in Kerr frequency combs. Such enhanced nonlinearity can be used to generate optical frequency combs if driven with two continuous-wave control and probe lasers and significantly reduce the threshold of nonlinear optical processes. The comb spacing can be well tuned by changing the frequency beating between the driving control and probe lasers. The proposed method is versatile and can be adopted to different types of resonators, such as microdisks, microspheres, microtoroids or microrings.
摘要：
Microstructure evolution and size effect of a two-dimensional barium titanate lattice sqaure have been studied using phase-field simulation. Based on the Landau phenomenological model, we calculated the microstructure evolution of the tetragonal and orthorhombic ferroelectric BaTiO3 started from a single domain with various lattice sizes. A direction-dependent hysteresis loop can be quantitatively described. The results show that both the phase transition with temperature and polarization switching under an external electric field are accompanied by multidomain and multiphase production in a large single-domain lattice, but synchronous changes in polarization in small lattice; As the grain size decreases, the orthorhombic -> tetragonal phase-transition temperature increased, while the tetragonal -> cubic, cubic -> tetragonal, and tetragonal -> orthorhombic phase-transition temperatures decrease. An interesting conclusion is that it shows triple hysteresis loops along the [11]-direction when the lattice size decreases to a certain size. The simulations of microstructure evolutions not only produce a good domain-switching process under various electric fields, but also provide a comprehensive microstructure evolution in the vicinity of the phase-transition points. The physics underlying the continuous evolution of microstructure with electric field and temperature is discussed. (C) 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
期刊：
Solid State Communications,2014年185:30-34 ISSN：0038-1098
通讯作者：
Huang, H. L.
作者机构：
[Huang, H. L.; Wu, Y. Y.; Sun, Z. Y.] Wuhan Polytech Univ, Sch Elect & Elect Engn, Wuhan 430000, Peoples R China.;[Wang, B.] ENN Grp Co Ltd, Langfang 065001, Hebei, Peoples R China.
通讯机构：
[Huang, H. L.] W;Wuhan Polytech Univ, Sch Elect & Elect Engn, Wuhan 430000, Peoples R China.
关键词：
A. Two-dimensional spin model;D. Bell inequality;D. Nonlocality;D. Phase transition
摘要：
In this paper, we use the Bell inequality to study the bipartite correlation in an exactly soluble two-dimensional Ising-Heisenberg spin system. The Bell inequality can detect not only the quantum phase transition, but also the thermal phase transitions, or the system. The property or bipartite correlation in the system is also analyzed. In the quantum anti-ferromagnetic phase, the Bell inequality is violated thus nonlocality is present. It is interesting that the nonlocality is enhanced by thermal fluctuation, and similar results have not been observed in anti-ferromagnetic phases. In the ferromagnetic phase, the quantum correlation turns out to be very novel, which cannot be captured by entanglement or nonlocality. (C) 2014 Elsevier Ltd. All rights reserved.
关键词：
2D atom localization;Probe absorption and gain;Standing wave
摘要：
A scheme of two-dimensional atom localization is proposed based on the phase-sensitive probe absorption and gain in a four-level atomic system with a closed-loop configuration. Due to the spatially dependent atom-field interaction, the position probability distribution of the atom can be directly determined by measuring the resulting absorption and gain spectra of the weak probe laser field. It is found that the phase-sensitive property of the atomic system significantly improves the localization behavior. Especially the maximal probability of finding the atom at a particular position within the sub-wavelength domain of the standing waves can arrive at unity by appropriate choice of the system parameters. (C) 2014 Elsevier B.V. All rights reserved.
摘要：
The ground state of interacting spin chains in external magnetic fields can undergo a quantum phase transition (QPT) characterized by dramatic changes at a critical value of the magnetic field. In this paper, we use Bell-type inequalities to study the multipartite correlations (including multipartite entanglement and multipartite nonlocality in an n-spin subsystem) in the QPT of an infinite XY chain. An efficient numerical optimization procedure is proposed to figure out the violation measure Mn of the inequalities. For n≤7, the magnetic-field ( λ) dependence of Mn is studied. We find the derivative of Mn is divergent exactly at the QPT point λc=1 for any n. In addition, with the increase of n, Mn converges quickly for λ<λc and converges very slowly for λ>λc, which can be regarded as another signal for the QPT. Furthermore, in the vicinity of λc, high-order Bell-type inequalities will be violated as long as n is large enough. This indicates that high-level multipartite correlation will be present when the system is in the vicinity of the QPT point. Nevertheless, genuine n-partite entanglement or genuine n-partite nonlocality is not observed in the QPT.
摘要：
In this paper, using the infinite time-evolving block decimation (iTEBD) algorithm and Bell-type inequalities, we investigate multipartite quantum nonlocality in an infinite one-dimensional quantum spin- 12 XXZ system. High hierarchy of multipartite nonlocality can be observed in the gapless phase of the model, while only the lowest hierarchy of multipartite nonlocality is observed in most regions of the gapped antiferromagnetic phase. Thereby, Bell-type inequalities disclose different correlation structures in the two phases of the system. Furthermore, at the infinite-order quantum phase transition (QPT, or Kosterlitz-Thouless QPT) point of the model, the correlation measures always show a local minimum value, regardless of the length of the subchains. It indicates that relatively low hierarchy of multipartite nonlocality would be observed at the infinite-order QPT point in a Bell-type experiment. The result is in contrast to the existing results of the second-order QPT in the one-dimensional XY model, where multipartite nonlocality with the highest hierarchy has been observed. Thus, multipartite nonlocality provides an alternative perspective to distinguish between these two kinds of QPTs. Reliable clues for the existence of tripartite quantum entanglement have also been found.
摘要：
A quantitative core-shell structure model on the grain size effects is applied to investigate the effect of grain size on the electrocaloric effect of BaTiO3 nanoparticles. In this study, considering the grain surface effects, the nanoparticle is composed of inner tetragonal core and surface cubic layer. Theoretical analysis indicates that the adiabatic temperature change peak is depressed and diffuse in BaTiO3 nanoparticles. With decreasing grain size, adiabatic temperature change peak moves to lower temperature. Moreover, it is worth noting that the maximum of adiabatic temperature change increases with the increase of the applied electric field gradient and decreases with the increase of the initial field. Crown Copyright (C) 2013 Published by Elsevier B.V. All rights reserved.
摘要：
Thermally induced optically distortion effects are one of the main impediments to be overcome in developing high power solid-state lasers. To compensate the dynamic aberration of laser beam, an intra-cavity adaptive optical system was developed. A beaconing light was introduced to measure the wavefront aberration of intracavity laser beam and a MEMS deformable mirror was used to improve the wavefront aberration and output power of the laser. A genetic algorithm was used to adjust the control voltages of 37 independent electrodes to vary the shape of the deformable mirror surface such that the aberration of laser beam can be compensated. The experimental result showed that the output power was increased nearly 3 times and the beam quality was improved obviously by closed loop automatic control of the adaptive optical system. (C) 2011 Elsevier GmbH. All rights reserved.
摘要：
The singularity of quantum correlation has been widely regarded as a valuable indicator for quantum phase transition (QPT) in low-dimensional quantum systems. In this paper, in a two-leg spin ladder with ring exchange, the critical points of the system cannot be detected by analyzing the singularity of the quantum discord (a kind of quantum correlation). Instead, the discord exhibits a novel odd-even effect in the symmetry-breaking (SB) regions, which can be used to detect the two critical points between the SB regions and the non-SB regions. The underlying mechanism of the odd-even effect is explained. (C) 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
摘要：
Bell inequalities and nonlocality have been widely studied in one-dimensional quantum systems. As a kind of quantum correlation, it is expected that bipartite nonlocality should be present in quantum systems, just as bipartite entanglement does. Surprisingly, for various models, two-qubit states do not violate Bell inequalities, i.e., they are local. Recently, it is realized that the results are related to the monogamy trade-off obeyed by bipartite Bell correlations, thus it is believed that for general translation invariant systems, two-qubit states should not violate the Bell inequality [Oliveira, Europhys. Lett. 100, 60004 (2012)]. In this Brief Report, we demonstrate that in perfect translation-invariant systems with an even number of sites, the Bell inequality can be violated. A nontrivial model is constructed to confirm the conclusion.
摘要：
Purpose - Denoising of the vibration signal is crucial to identify a structure's damage. Based on noise frequency character, the "real" vibration signal can be gotten. The purpose of this paper is to propose a novel method for denoising a signal based on the wavelet transform. Design/methodology/approach - The vibration signal with noise which can be collected by wireless network is decomposed by wavelet transform. In order to select optimal level of wavelet decomposition, based on noise's frequency, power spectral density is used. A soft thresholding method based on minimum mean-variance is used for vibration signal de-noising with Gaussian noise. Findings - A novel method has been described in his paper. Based on the relationship between vibration signal's character and noise frequency, the way to get rid of noise is combined wavelet transform with power spectral density. Originality/value - In order to select optimal level of wavelet decomposition, based on noise's frequency, power spectral density is used. A soft thresholding method based on minimum mean-variance is used for vibration signal denoising with Gaussian noise.
