Institute of Theoretical Physics, Ecole Polytechnique Fédérale de Lausanne EPFL, CH-1015 Lausanne, Switzerland.
Phys Rev Lett. 2011 Mar 18;106(11):110403. doi: 10.1103/PhysRevLett.106.110403. Epub 2011 Mar 16.
We investigate the crossover from Bardeen-Cooper-Schrieffer (BCS) superfluidity to Bose-Einstein condensation (BEC) in a two-dimensional Fermi gas at T=0 using the fixed-node diffusion Monte Carlo method. We calculate the equation of state and the gap parameter as a function of the interaction strength, observing large deviations compared to mean-field predictions. In the BEC regime our results show the important role of dimer-dimer and atom-dimer interaction effects that are completely neglected in the mean-field picture. Results on Tan's contact parameter associated with short-range physics are also reported along the BCS-BEC crossover.
我们使用固定节点扩散蒙特卡罗方法研究了二维费米气体中从 Bardeen-Cooper-Schrieffer（BCS）超流到玻色-爱因斯坦凝聚（BEC）的交叉。我们计算了状态方程和间隙参数作为相互作用强度的函数，观察到与平均场预测相比存在较大偏差。在 BEC 区域，我们的结果表明了二聚体-二聚体和原子-二聚体相互作用效应的重要性，而这些效应对平均场图像来说是完全忽略的。我们还报告了与短程物理有关的 Tan 接触参数在 BCS-BEC 交叉区域的结果。
