基于相对论平均场有效对力的中子物质BCS-BEC渡越  

BCS-BEC Crossover in Neutron Matter with RMF Effective Pairing Interaction

作　　者：孙保元[1,2] 郭安良 钱庄 SUN Baoyuan;GUO Anliang;QIAN Zhuang(School of Nuclear Science and Technology,Lanzhou University,Lanzhou 730000,China;Engineering Research Center for Neutron Application Technology,Ministry of Education, Lanzhou University,Lanzhou 730000,China)

机构地区：[1]兰州大学核科学与技术学院,兰州730000 [2]兰州大学中子应用技术教育部工程研究中心,兰州730000

出　　处：《原子核物理评论》2018年第4期505-510,共6页Nuclear Physics Review

基　　金：国家自然科学基金资助项目(11875152)~~

摘　　要：基于核物质的相对论Hartree-Bogoliubov(RHB)理论,采用相对论平均场单玻色子交换形式的有效对相互作用,研究了不同对力强度下双中子关联及其中的BCS-BEC渡越现象。通过引入有效衰减因子χ调节对力强度,定量分析费米面处中子对能隙和单粒子动能比值?Fn/eFn及无量纲参数1/(kFna)随费米动量kFn的演化行为,发现双中子对在χ=0.51时进入BCS-BEC渡越区域,在χ=0.67时可达到幺正极限。进而分析了中子对能隙、中子对波函数及相干长度等物理量在相应临界点处的特征,并给出渡越时双中子短程关联概率的定量判据。发现当配对中子处于平均中子间距以内的概率P(dn)0.80时,双中子对从纯BCS耦合过渡到BCS-BEC渡越区域。Based on the relativistic Hartree-Bogoliubov theory in nuclear matter, the dineutron correlations and the crossover from Bardeen-Cooper-Schrieffer(BCS) region of neutron Cooper pairs to Bose-Einstein condensation(BEC) are investigated with the one-boson-exchange type of pairing force generated from the relativistic mean field(RMF) model. By introducing an effective factor χ in the RMF effective pairing interaction, the density dependence of the ratios between neutron pairing gap at Fermi surface and neutron Fermi kinetic energy ?Fn/eFnand the dimensionless parameter 1/(kFna) are analyzed quantitatively. Then the criteria where dineutron correlations exactly reach the threshold of BCS-BEC crossover or unitary limit are determined to beχ=0.51 or 0.67, respectively. In addition, features of neutron pairing gap, Cooper pair wave function and dineutron coherence length are illustrated, and the value of the probability for partner neutrons correlated within the average inter-neutron distance, namely P(dn) 0.80, is obtained as a criterion of BCS-BEC crossover.

关 键 词：对关联 BCS-BEC渡越 核物质 有效对力 相对论平均场 

分 类 号：O572.21[理学—粒子物理与原子核物理]