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Tunneling and Self-Trapping of Superfluid Fermi Gases in bcs-bec crossover

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Communications in Theoretical Physics 2012年第2期57卷 188-194页

作者：周昱王颖罗文琛马晓栋 Department of Physics Jiangsu University of Science and Technology Department of Physics East China Normal University Departement de Physique Universite de SherbrookeSherbrookeQuebec J1K 2R1Canada Department of Physics Xinjiang Normal UniversityUrumuchi 830054China

We investigate tunneling and self-trapping of superfluid Fermi gases under a two-mode ansatz in different regimes of the crossover from Bardeen-Cooper-Schrieffer （bcs） superfluid to Bose-Einstein condensates （bec）. Starting from a generalized equation of state, we derive the coupled equations of relative atom-pair number and relative phase about superfluid Fermi gases in a double-well system and then classify the different oscillation behaviors by the tunneling strength and interactions between atoms. Tunneling and self-trapping behaviors are considered in the whole bcs-bec crossover in the ease of a symmetric double-well potential. We show that the nonlinear interaction between atoms makes the self-trapping more easily realized in bcs regime than in the bec regime and stability analysis is also given.

关键词： bcs-bec crossover Josephson effect macroscopic quantum self-trapping

Condensate fraction of asymmetric three-component Fermi gas

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Chinese Physics B 2014年第2期23卷 106-111页

作者：杜佳佳梁军军梁九卿 Institute of Theoretical Physics Shanxi University Department of Physics Shanxi University

In this paper, we investigate the condensate fraction （CF） of fermionic pairs in the bcs-bec crossover for three- component Fermi gas with both asymmetric interactions and unequal chemical potentials in two-dimensional free space. By using the functional-path-integral method, we have analytically derived the number densities and bound-state energy, from which the off-diagonal long-range order is analyzed in terms of the asymptotic behavior of the two-body density matrix. The explicit formula of CF is obtained as a function of the bound-state energy and population imbalance. It is demonstrated that the CF spectrum with respect to the bound-state energy can be used to characterize the quantum phase transition between the two kinds of Sarma phases as well as the transition from three-component to two-component superfluid. Moreover we obtain the same analytic formula of CF in the bcs superfluid phase as that of homogeneous Fermi gas with equal chemical potentials.

关键词： condensate fraction bcs-bec crossover Sarma phases

First and Second Sound Modes in a Uniform Fermi Gas

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Chinese Physics Letters 2009年第7期26卷 25-28页

作者：黄备兵完绍龙 Institute for Theoretical Physics and Department of Modern Physics University of Science and Technology of China Hefei 230026

First and second sound modes in a uniform fermionic atom gas with Feshbaeh resonance are investigated in the frame of a two-fluid model at finite temperature. All thermodynamic quantities axe calculated for a given thermodynamic potential. The analytical results for thermodynamic quantities and sound velocities in bcs and bec limits are obtained. The numerical results show that there exists a continuous interpolation for sound velocities of the first and second sound modes at fixed T/Tc between bcs and bec limits. The existence of the second sound mode indicates the existence of superfluidity.

关键词： HIGH-TEMPERATURE SUPERCONDUCTORS bcs-bec crossover HELIUM II

Some Recent Progress on Quark Pairings in Dense Quark and Nuclear Matter

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Communications in Theoretical Physics 2012年第2期57卷 251-270页

作者：庞锦毅王金成王群 Department of Modern Physics University of Science and Technology of China

In this review article we give a brief overview on some recent progress in quark pairings in dense quark/nuclear matter mostly developed in the past five *** focus on following aspects in particular:the bcs-bec crossover in the CSC phase,the baryon formation and dissociation in dense quark/nuclear matter,the Ginzburg-Landau theory for three-flavor dense matter with UA(1) anomaly,and the collective and Nambu-Goldstone modes for the spin-one CSC.

关键词： color superconductivity bcs-bec crossover baryon formation and dissociation Ginzburg-Landau theory

Bose-Einstein Condensation in Strong-Coupling Quark Color Superconductor near Flavor SU(3) Limit

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Communications in Theoretical Physics 2011年第6期55卷 1065-1072页

作者：张小兵任春福张一 School of Physics Nankai University Department of Physics Shanghai Normal University

Near the flavor SU（3） limit, we propose an analytical description for color-flavor-locked-type Bardeen- Cooper-Schrieffer （bcs） phase in the Nambu Jona-Lasinio （NJL） model. The diquark behaviors in light-flavor and strange-flavor-involved channels and Bose-Einstein condensation （bec） of bound diquark states are studied. When the attractive interaction between quarks is strong enough, a bcs-bec crossover is predicted in the environment with color-flavor-locked pairing pattern. The resulting Bose-Einstein condensed phase is found to be an intergrade phase before the emergence of the previous-predicted bec phase in two-flavor quark superconductor.

关键词： color superconductor color-flavor-locked phase bcs-bec crossover

Finite dimensional global and exponential attractors for a class of coupled time-dependent Ginzburg-Landau equations

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Science China Mathematics 2012年第1期55卷 141-157页

作者： JIANG Jie WU Hao GUO BoLing Institute of Applied Physics and Computational Mathematics Beijing 100088 China School of Mathematical Sciences and Shanghai Key Laboratory for Contemporary Applied Mathematics Fudan University Shanghai 200433 China

We study a coupled nonlinear evolution system arising from the Ginzburg-Landau theory for atomic Fermi gases near the bcs (Bardeen-Cooper-Schrieffer)-bec (Bose-Einstein condensation) ***,we prove that the initial boundary value problem generates a strongly continuous semigroup on a suitable phase-space which possesses a global *** we establish the existence of an exponential *** a consequence,we show that the global attractor is of finite fractal dimension.

关键词： time-dependent Ginzburg-Landau equations bcs-bec crossover global attractor exponentialattractor

bcs-bec交叉区域囚禁费米凝聚体基态与激发谱的理论研究

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BCS-BEC交叉区域囚禁费米凝聚体基态与激发谱的理论研究

作者：王成涛复旦大学

学位级别：硕士

随着Feshbach共振技术的飞速发展,超冷囚禁费米凝聚体在bcs-bec交叉区域的研究引起了物理学家们极大的兴趣。从著名的bcs超导理论和bec超流理论出发,现已大致清楚了该体系的物理图像。本文首先回顾了对bcs-bec交叉区域研究的进展。基于... 详细信息

随着Feshbach共振技术的飞速发展,超冷囚禁费米凝聚体在bcs-bec交叉区域的研究引起了物理学家们极大的兴趣。从著名的bcs超导理论和bec超流理论出发,现已大致清楚了该体系的物理图像。本文首先回顾了对bcs-bec交叉区域研究的进展。基于一个全新的状态方程和基态波函数满足的广义Gross-Pitaevskii(GP)方程,用变分法求解非线性广义GP方程,得到基态波函数和化学势。体系的激发态满足广义Bogoliubov-de Gennes(BdG)方程组。本文的主要方法是选取三维轴对称谐振子波函数为基矢,对激发态波函数进行展开,并通过引入泡利矩阵,将求解广义BdG方程组转化成求解广义特征值问题,使问题变得简单易解。本文的特点是体系的基态采用解析分析,而激发态采用数值计算的方法。状态方程及其多方指数,化学势和基态波函数的理论曲线均显示了体系的基态性质。在解析计算无法涉及到的参数范围内,给出了较低的几个能谱随体系参数变化的数值曲线,并在与实验和其它方法所得结果进行比较时发现,这些数值结果显示了体系的激发态性质。

关键词：囚禁费米凝聚体 bcs-bec crossover 广义BdG方程组