发表机构
Institute of Modern Physics, Northwest University; School of Physics, Northwest University; Shaanxi Key Laboratory for Theoretical Physics Frontiers; Fundamental Discipline Research Center for Quantum Science and Technology of Shaanxi Province; Hefei National Laboratory（西北大学现代物理研究所; 西北大学物理学院; 陕西理论物理前沿重点实验室; 陕西省量子科学与技术基础学科研究中心; 合肥国家实验室）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
该研究通过辅助场量子蒙特卡洛方法系统研究了二维吸引性哈伯德模型中BCS-BEC渡越的配对序与凝聚分数，提供了全面的无偏数值基准。
AI 中文摘要
我们报告了使用数值精确的辅助场量子蒙特卡洛方法对二维吸引性哈伯德模型中超导基态的系统研究。我们主要关注跨越BCS-BEC渡越的配对序和凝聚分数。我们的数值计算覆盖了广泛且物理相关的参数区间，其中相互作用强度$U/t=2\sim 12$（$t$为最近邻跳跃振幅）和费米子密度$n=0.25\sim 1.0$。我们系统地刻画了配对序和凝聚分数对相互作用强度和费米子密度的依赖关系，并进行了有限尺寸外推以获得它们在热力学极限下的值。作为补充量，我们还提供了双占据数和总能量的高精度数值结果。此外，我们研究了次近邻跳跃对模型超导性质的影响。我们的结果为吸引性哈伯德模型提供了一套全面的无偏数值数据，为理解跨越BCS-BEC渡越的超导性以及验证未来的理论和数值方法建立了定量基准。
英文摘要
We report a systematic study of the superconducting ground state in the two-dimensional attractive Hubbard model, employing the {\it numerically exact} auxiliary-field quantum Monte Carlo method. We focus primarily on the pairing order and condensate fraction across the BCS-BEC crossover. Our numerical calculations cover a broad and physically relevant parameter regime, with the interaction strength $U/t=2\sim 12$ (where $t$ is the nearest-neighbor hopping amplitude) and fermion density $n=0.25\sim 1.0$. We systematically characterize the dependence of the pairing order and condensate fraction on both the interaction strength and fermion density, and perform finite-size extrapolations to obtain their thermodynamic-limit values. As complementary quantities, we also provide high-precision numerical results for the double occupancy and total energy. Furthermore, we investigate the effects of next-nearest-neighbor hopping on the superconducting properties of the model. Our results offer a comprehensive set of unbiased numerical data for the attractive Hubbard model, establishing quantitative benchmarks for understanding superconductivity across the BCS-BEC crossover and for validating future theoretical and numerical approaches.
Comments13 pages, 13 figures (with Appendixes)
