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ΔFn/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.
Abstract:
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 ΔFn/eFn and 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 be χ=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.
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