共查询到20条相似文献,搜索用时 62 毫秒
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研究了一维光晶格中超流费米气体的能隙孤子. 应用平均场理论和超流费米气体的流体动力学模型, 利用变分法得到了在整个跨越区超流费米气体在光晶格中存在带隙孤子的条件, 即原子间的非线性相互作用项与系统化学势以及晶格深度的相互关系. 通过对超流费米气体的基态能隙孤子空间分布的分析与对比, 揭示了在一维情况下超流费米气体能隙孤子的存在并发现超流费米气体能隙孤子在整个跨越区当系统从Bose-Einstein凝聚端跨越到BCS端时孤子存在的条件与孤子空间分布存在明显的差别. 相似文献
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平面波导环形格子结构型光交错复用器的设计 总被引:2,自引:0,他引:2
在分析比较双折射晶体偏振光干涉型和平面波导环形格子结构型光交错复用滤波器原理的基础上,揭示了两者在光谱透射率的数学上的等效性,给出了两者结构参量之间的等效关系,可以直接利用经简单傅里叶级数对比法获得的晶体的结构参量对平面波导环形格子结构型光交错复用滤波器进行结构设计。利用该方法对一个两级平面波导环形格子结构型光交错复用滤波器进行了优化设计,信道隔离度比文献中结构提高了近5dB,而且结构参量有多种组合。与利用复杂的格子理论计算仅获得一组结构参量相比,该方法更加简单、有效。 相似文献
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表面缺陷基态模孤子的性质在实现全光控制方面有重要的应用。基于非线性薛定谔方程,利用虚时间变换、非线性松弛法以及分步傅里叶算法等数值方法对具有半无限缺陷光格子的克尔型非线性介质中存在的基态模的特性进行了详细研究。研究结果表明:对于吸引型半无限缺陷光格子,表面缺陷基态模只能分布于缺陷处,而对于排斥型半无限缺陷光格子,表面缺陷基态模既可以分布于缺陷处,也可以分布于其他格子通道处;每个系统参数存在着一个临界值,当其他参数保持不变的情况下,这个系统参数的数值大于或小于其临界值时,表面缺陷基态模将能或不能分布于缺陷处。从物理机制方面看,光格子与光束诱导的非线性折射率之间的竞争导致了这种临界行为的出现。 相似文献
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超导体中磁通线及超流He中涡旋线的存在,早已为人们所熟知.它们的结构是简单的,都是在直径约为相干长度的正常态的芯子外面环以超流,具有轴对称性.磁通线的磁通量和涡旋线的环量都是量子化的,分别为一个磁通量子和环量量子,这是在超导体及超流4He中特有的宏观量子现象.1972年发现的液体3He的超流相,虽然是一种新型的超流相,但由于它的宏观量子性,人们自然地认为会有涡旋线存在,这已为后来的实验所证实. 近两年利用赫尔辛基低温实验室中能达到mK温度的旋转恒温器,芬兰和苏联的科学家发现了两个完全出乎人们意料的结果.这是在旋转的超流液体… 相似文献
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The atomic Bose gas is studied across a Feshbach resonance, mapping out its phase diagram, and computing its thermodynamics and excitation spectra. It is shown that such a degenerate gas admits two distinct atomic and molecular superfluid phases, with the latter distinguished by the absence of atomic off-diagonal long-range order, gapped atomic excitations, and deconfined atomic π-vortices. The properties of the molecular superfluid are explored, and it is shown that across a Feshbach resonance it undergoes a quantum Ising transition to the atomic superfluid, where both atoms and molecules are condensed. In addition to its distinct thermodynamic signatures and deconfined half-vortices, in a trap a molecular superfluid should be identifiable by the absence of an atomic condensate peak and the presence of a molecular one. 相似文献
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当前在冷原子和玻色爱因斯坦凝聚(BEC)领域的一个重要问题是在Feshbach共振附近的冷费米气体如何从BEC态演变到BCS(Bardeen Schrieffer Cooper)态.本文进一步研究在Feshbach共振附近超流态的相滑移现象.通过具体的数值计算,给出了费米气体在相滑移时的粒子数密度的分布,并对不同温度下的相滑移的大小进行了分析.结果表明,相滑移现象可以作为实验上判断系统是否处于超流态的一个可行的判据.
关键词:
超流费米气体
相滑移
Feshbach共振 相似文献
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We study the quark-antiquark scattering phase shift and meson spectral function in the pion superfluid described by the Nambu-Jona-Lasinio model. Meson mixing in the pion superfluid dramatically changes the full scattering phase shift and significantly broadens the spectral function of some collective modes. 相似文献
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The gapless Weyl superfluid has been widely studied in the three-dimensional ultracold fermionic superfluid.In contrast to Weyl superfluid, there exists another kind of gapless superfluid with topologically protected nodal lines,which can be regarded as the superfluid counterpart of nodal line semimetal in the condensed matter physics, just as Weyl superfluid with Weyl semimetal. In this paper we study the ground states of the cold fermionic gases in cubic optical lattices with one-dimensional spin-orbit coupling and transverse Zeeman field and map out the topological phase diagram of the system. We demonstrate that in addition to a fully gapped topologically trivial phase, some different nodal line superfluid phases appear when the Zeeman field is adjusted. The presence of topologically stable nodal lines implies the dispersionless zero-energy flat band in a finite region of the surface Brillouin zone. Experimentally these nodal line superfluid states can be detected via the momentum-resolved radio-frequency spectroscopy. The nodal line topological superfluid provide fertile grounds for exploring exotic quantum matters in the context of ultracold atoms. 相似文献
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Topological superfluid state is different from the normal superfluid one due to the excitation energy gap on the boundary. How to obtain the topological superfluid state by using spin-orbit coupling to control the s-waves paired mass-imbalanced Fermi gas is a recent novel topic. In this paper, we study the topological superfluid phase diagram of two-dimensional mass-imbalanced Fermi gas with Rashba spin-orbit coupling at zero temperature. We find that due to the competition among mass imbalance, pairing interaction and spin-orbit coupling, there is a double-well structure in the thermodynamic potential, which affects the properties of the ground state of the system. We comprehensively give the phase diagrams of the system on the plane of spin-orbit coupling and chemical potential, and the phase diagrams on the plane of the reduced mass ratio and two-body binding energy. This study not only points out the stable region of topological superfluid state of mass-imbalanced Fermi gas, but also provides a detailed theoretical basis for better observation of topological superfluid state in experiments. 相似文献
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YongHao Huang QiYuan Pan Wei-Liang Qian JiLiang Jing ShiLiang Wang 《中国科学:物理学 力学 天文学(英文版)》2020,(3):33-43
In this work,we study the effects of the Weyl corrections on the p-wave superfluid phase transition in terms of an EinsteinMaxwell theory coupled to a complex vector field.In the probe limit,it is observed that the phase structure is significantly modified owing to the presence of the higher order Weyl corrections.The latter,in general,facilitates the emergence of the superfluid phase as the condensate increases with the Weyl coupling measured byγ.Moreover,several features about the phase structure of the holographic superfluid are carefully investigated.In a specific region,the phase transition from the normal phase to the superfluid phase is identified to be the first order,instead of being the second order,as in the cases for many holographic superconductors.By carrying out a numerical scan of model parameters,the boundary dividing these two types of transitions is located and shown to be rather sensitive to the strength of Weyl coupling.Also,a feature known as"Cave of Winds",associated with the emergence of a second superfluid phase,is observed for specific choices of model parameters.However,it becomes less prominent and eventually disappears asγincreases.Furthermore,for temperature in the vicinity of the critical one for vanishing superfluid velocity,denoted by T0,the supercurrent is found to be independent of the Weyl coupling.The calculated ratio,of the condensate with vanishing superfluid velocity to that with maximal superfluid velocity,is in good agreement with that predicted by Ginzburg-Landau theory.While compared with the impact on the phase structure owing to the higher curvature corrections,the findings in our present study demonstrate entirely different characteristics.Further implications are discussed. 相似文献
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Two-dimensional (p(x)+ip(y)) superfluids or superconductors offer a playground for studying intriguing physics such as quantum teleportation, non-Abelian statistics, and topological quantum computation. Creating such a superfluid in cold fermionic atom optical traps using p-wave Feshbach resonance is turning out to be challenging. Here we propose a method to create a p(x)+ip(y) superfluid directly from an s-wave interaction making use of a topological Berry phase, which can be artificially generated. We discuss ways to detect the spontaneous Hall mass current, which acts as a diagnostic for the chiral p-wave superfluid. 相似文献
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T. Fliessbach 《Il Nuovo Cimento D》1991,13(2):211-231
Summary Guided by the analogy to the Bose-Einstein condensation of the ideal Bose gas (IBG) we propose a new model for the λ-transition
of liquid helium. Deviating from the IBG our model uses phase-ordered and localized single-particle functions. This means
that finite groups of particles are assumed to be phase-locked. These phase correlations can be related to the singularity
at the transition point and to the occurrence of the superfluid density. The model leads to the following results: 1) a possible
explanation of the logarithmic singularity of the specific heat, 2) a characteristic functional form for the superfluid density
which yield excellent fits to the experimental data, 3) a quantitative prediction of a small nonzero entropy content of the
superfluid component. 相似文献