跨越BCS-BEC渡越的交替磁性
Altermagnetism across the BCS-BEC crossover
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中文总结 AI 辅助
本研究通过二维配对费米系统，揭示了交替磁性在BCS-BEC渡越中导致相位刚度普适二次方抑制，并引发有限动量配对不稳定性，为比较两侧配对破坏提供了简单模型。
中文摘要 AI 辅助
我们研究了一个二维配对费米系统，其中交替磁性产生依赖于动量的自旋劈裂。相互作用强度通过两体束缚能来描述，使得化学势和配对能隙在固定密度下从弱耦合的巴丁-库珀-施里弗（BCS）区域到强耦合的玻色-爱因斯坦凝聚（BEC）区域自洽演化。通过给配对一个小的质心动量并跟踪由此产生的自由能变化，我们检验了均匀配对态的稳定性。我们表明，在零温度下，相位刚度遵循普适的二次方抑制关系，$J/J_0 = 1 - (\alpha/\alpha_0)^2$，跨越整个完全有能隙的渡越区域。仅当BCS侧出现无能隙的玻戈留波夫口袋时，才会偏离这一关系，这些口袋迅速降低刚度，并可能触发向有限动量配对的不稳定性。在BEC区域，这一普适二次方修正对应于紧密束缚复合玻色子的有效质量改变。因此，该模型提供了一个简单的设置，用于比较渡越两侧BCS和BEC上的交替磁性配对破坏。
英文摘要
We study a two-dimensional paired Fermi system in which altermagnetism produces a spin splitting that depends on momentum. The interaction strength is described through the two-body binding energy, so that the chemical potential and pairing gap evolve self-consistently from the weak-coupling Bardeen-Cooper-Schrieffer (BCS) regime to the strong-coupling Bose-Einstein-condensate (BEC) regime at fixed density. The stability of the uniform paired state is examined by giving the pairs a small center-of-mass momentum and following the resulting change in free energy. We show that at zero temperature, the phase stiffness follows a universal quadratic suppression, $J/J_0 = 1 - (α/α_0)^2$, across the entire fully gapped crossover regime. Deviations from this relation emerge only on the BCS side upon the opening of gapless Bogoliubov pockets, which rapidly reduce the stiffness and can trigger an instability toward finite-momentum pairing. In the BEC regime, this universal quadratic correction corresponds to the altered effective mass of the tightly bound composite bosons. The model therefore provides a simple setting in which to compare altermagnetic pair breaking on the BCS and BEC sides of the crossover.
发表机构
- University of Sassari（萨萨里大学）
- Università di Padova（帕多瓦大学）
- INFN Sezione di Padova（意大利国家核物理研究所帕多瓦分部）
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