共查询到20条相似文献,搜索用时 140 毫秒
1.
利用能量泛函变分法研究了一维Bose-Fermi系统稳定基态的存在条件.根据Bose-Fermi系统的Lagrange量可以得到三维Bose-Fermi体系所满足的非线性动力学方程组.当外势阱的横向囚禁频率远大于轴向囚禁频率时,体系可以当作一维模型来处理.从描述三维体系的动力学方程可以得到描述一维体系的动力学方程,选取适当的无量纲参数,可以对一维动力学方程组进行无量纲处理,得到数值计算和理论分析中常用到的无量纲方程.选择高斯型试探解(简单孤立子解),利用能量泛函变分法得到一维Bose-Fermi体系稳定的
关键词:
Bose-Fermi
稳定性
基态
临界条件 相似文献
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研究了平面Bessel型光晶格(BL)中双组分玻色-爱因斯坦凝聚(BECs)体系的基态解.从描述三维(3D)BECs体系的动力学方程Gross-Pitaevskii方程(GPE)出发,当垂直方向囚禁频率远大于平面上囚禁频率时,得到了描述2D-BECs体系的动力学方程.利用双组分BECs体系中原子之间相互作用与BL强度相互平衡的条件,得到了平面BL光晶格中2D-GPE的一组基态精确解,给出了基态的原子数分布,总原子数和能量与原子之间相互作用强度及BL势的关系.相对于单组分BEC体系,由于不同组分原子相互作用的存在,使得BL光晶格中双组分BECs基态具有更丰富的结构.当不存在不同组分原子之间的相互作用时,模型简化到单组分体系,并给出了相应的基态解,原子数分布和能量.
关键词:
Bessel型光晶格
基态解
双组分玻色-爱因斯坦凝聚 相似文献
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研究了一维光晶格中超流Fermi气体基态解的性质.在平均场理论框架下,利用超流Fermi体系中原子间相互作用能与晶格势能相互平衡的条件,得到了一维光晶格中超流Fermi气体在整个BEC-BCS跨越区的一组基态解,给出了基态的原子数密度空间分布、总原子数和能量.进一步对系统从BEC端转变到BCS端时的基态解性质进行了深入分析和对比.结果表明,一维光晶格中超流Fermi气体基态分布具有一些特殊的性质,由于Fermi压力,相比而言超流Fermi气体在BCS端的基态原子数密度空间分布较为扩展,平均能量明显偏高. 相似文献
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基于Gross-Pitaevskii(G-P)平均场能量泛函和变分方法,对囚禁在谐振势阱中的玻色凝聚气体,在T=0K时的基态波函数提出一种新解法.运用这一方法能得到基态波函数的解析表达式,求解出系统的化学势与凝聚原子数的关系等.其结果与Edwards和Dalfovo等人直接数值求解G-P方程所得到的结果相一致,并在Nas/a1大原子数N的极限条件下,与托马斯-费米近似模型的结论也趋向一致.该方法计算简单,而且能够进行解析处理.
关键词:
玻色凝聚气体
G-P泛函
谐振势阱
基态波函数 相似文献
7.
对囚禁在轴对称谐振势阱中的玻色凝聚气体,提出一种新的试探波函数,运用Gross-Pitaevskii(G-P)平均场能量泛函和变分的方法,得到玻色凝聚气体基态和单涡旋态波函数的解析表达式,并计算出凝聚原子的平均能量、原子云轴向和径向尺度比,以及产生单涡旋态的临界角速度等重要物理量与凝聚原子数N之间的关系.其结果与Dalfovo等人直接数值求解G-P方程所得到的结果相一致.
关键词:
玻色凝聚气体
G-P泛函
波函数
谐振势阱 相似文献
8.
利用变分法和数值计算方法研究了二维线性和非线性光晶格中二维玻色-爱因斯坦凝聚体系中物质波孤立子的存在及其稳定性. 利用定态变分原理及Vakhitov-Kolokolov判据总结了线性和非线性结合光晶格中几种参数组合下定态定域解的稳定性. 结果表明, 当存在二维非线性光晶格时, 在吸引和排斥相互作用的原子体系中均可以存在稳定的物质波孤立子. 另外, 利用含时变分法研究了线性和非线性光晶格中物质波孤立子随时间的传播特性, 使波包参数对时间的一阶导数等于零, 可以给出稳定状态对应的参数, 结论和定态变分法给出的结果一致. 最后用数值计算方法研究变分结果的正确性, 把变分结果作为初始条件代入Gross-Pitaevskii方程研究其随时间传播特征, 得到了稳定的传播过程, 所得到的结果和变分分析结果一致.
关键词:
线性非线性光晶格
玻色-爱因斯坦凝聚
孤立子
稳定性 相似文献
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提出一种基于自旋相干态变换求解自旋-玻色模型基态的变分法, 并将其用于单原子模型, 得到旋波近似和非旋波近似情形下的解析基态能量和波函数, 特别是在光场与原子的弱、强耦合区域都与数值对角化结果符合得很好. 另外, 该方法也可以直接用于求解任意原子数的Dicke模型基态和相应的量子相变研究, 而通常基于Holstein-Primakoff变换的变分法, 原则上只适用于原子数趋于无穷的热力学极限情形.
关键词:
自旋相干态
变分法
J-C模型 相似文献
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S. Röthel A. Pelster 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,59(3):343-356
We analyze in detail recent experiments on ultracold dilute 87Rb–40K mixtures in Hamburg and in Florence within a mean-field theory. To this end we determine how the stationary bosonic and
fermionic density profiles in this mixture depend in the Thomas-Fermi limit on the respective particle numbers. Furthermore,
we investigate how the observed stability of the Bose-Fermi mixture with respect to collapse is crucially related to the value
of the interspecies s-wave scattering length. 相似文献
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We study the topological properties of a one-dimensional (1D) hardcore Bose-Fermi mixture using the exact diagonalization method. We firstly add a hardcore boson to a fermionic system and by examining the edge states we find that the quasi-particle manifests the topological properties of the system. Then we study a mixture with 7 fermions and 1 boson. We find that the mixture also exhibits topological properties and its behaviors are similar to that of the corresponding fermionic system. We present a qualitative explanation to understand such behaviors using the mapping between a hardcore boson and a spinless fermion. These results show the existence of topological properties in a 1D hardcore Bose-Fermi mixture and may be realized using cold atoms trapped in optical lattices experimentally. 相似文献
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We consider atomic Bose-Fermi mixtures in optical lattices and study the superfluidity of fermionic atoms due to s-wave pairing induced by boson-fermion interactions. We prove that the induced fermion-fermion coupling is always attractive if the boson-boson on-site interaction is repulsive, and predict the existence of an enhanced BEC-BCS crossover as the strength of the lattice potential is varied. We show that for direct on-site fermion-fermion repulsion, the induced attraction can give rise to superfluidity via s-wave pairing at striking variance with the case of pure systems of fermionic atoms with direct repulsive interactions. 相似文献
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In this paper we develop a variational theory to study the dynamicproperties of ultracold Bose gas in a funnel external potential. We obtain one-dimensional nonlinear equation which describes the dynamics of transverse tight confined bosonic gas from three-dimension to one-dimension, and find one-dimensional s-wave scattering length which depends on the shape oftransverse confining potential. If the funnel trapping potential is strong enough at zero temperature, all transverse excitations are frozen. We find the dynamic equation which describes the Tonks-Girardeau gas and present a qualitative analysis of the experimental accessibility of the Tonks-Girardeau gas with funnel-trapped alkalic atoms. 相似文献
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Zirbel JJ Ni KK Ospelkaus S D'Incao JP Wieman CE Ye J Jin DS 《Physical review letters》2008,100(14):143201
Using a Feshbach resonance, we create ultracold fermionic molecules starting from a Bose-Fermi atom gas mixture. The resulting mixture of atoms and weakly bound molecules provides a rich system for studying few-body collisions because of the variety of atomic collision partners for molecules; either bosonic, fermionic, or distinguishable atoms. Inelastic loss of the molecules near the Feshbach resonance is dramatically affected by the quantum statistics of the colliding particles and the scattering length. In particular, we observe a molecule lifetime as long as 100 ms near the Feshbach resonance. 相似文献
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Measurement of S-Wave Scattering Length between ~6Li and ~(88)Sr Atoms Using Interspecies Thermalization in an Optical Dipole Trap 下载免费PDF全文
We report the creation of the first mixture of ~6 Li and ~(88) Sr atoms in an optical dipole trap. Using this mixture,a measurement of the interspecies thermalization process is carried out and the previously unknown interspecies s-wave scattering length between ~6 Li and ~(88) Sr atoms is extracted to be |~(a6) Li-~(88) Sr| =(380_(-100)~(+160))a_0 with a_0 being the Bohr radius from the rate of interspecies thermalization. 相似文献
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本文基于参考文献[5]构建的精确的基态Mg_2的势能曲线,应用变相法对超冷温度下Mg原子的弹性散射特性进行了系统的研究.计算得到Mg原子碰撞的散射长度和有效力程分别为25.9a_0和191.3a_0,其中a_0是玻尔半径;低能极限下镁原子间的弹性碰撞主要为s-波碰撞,同时计算得到的基态Mg_2支持束缚态的数目为19.计算结果与文献[5]和Numerov法所得结果一致. 相似文献
19.
Ivanov VV Khramov A Hansen AH Dowd WH Münchow F Jamison AO Gupta S 《Physical review letters》2011,106(15):153201
We report on the realization of a stable mixture of ultracold lithium and ytterbium atoms confined in a far-off-resonance optical dipole trap. We observe sympathetic cooling of 6Li by 174Yb and extract the s-wave scattering length magnitude |a(6Li-174Yb)|=(13±3)a0 from the rate of interspecies thermalization. Using forced evaporative cooling of 174Yb, we achieve reduction of the 6Li temperature to below the Fermi temperature, purely through interspecies sympathetic cooling. 相似文献
20.
We show the emergence of a strongly interacting Bose-Fermi mixture from a two-component Fermi mixture with population imbalance. By analyzing in situ density profiles of 6Li atoms in the BCS-BEC crossover regime, we identify a critical interaction strength, beyond which all minority atoms pair up with majority atoms and form a Bose condensate. This is the regime where the system can be effectively described as a boson-fermion mixture. We determine the dimer-fermion and dimer-dimer scattering lengths and beyond-mean-field contributions. Our study realizes a gedanken experiment of bosons immersed in a Fermi sea of one of their constituents, revealing the composite nature of the bosons. 相似文献