BCS-BEC Crossover in Neutron Matter with RMF Effective Pairing Interaction
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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/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.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 △Fn/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.-
Key words:
- Pairing correlation /
- BCS-BEC crossover /
- nuclear matter /
- effetive pairing force /
- RMF
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