基于非交叉近似的非平衡动力学平均场计算及其推广
Nonequilibrium dynamical mean-field calculations based on the non-crossing approximation and its generalizations
摘要：
本文利用原子极限附近的自洽微扰展开，解决了哈伯德模型的非平衡动力学平均场论中的杂质问题。虽然最低阶，称为非交叉近似（NCA），是可靠的，只有当相互作用U是远远大于带宽，低阶修正的NCA原来是足以重现数值精确的蒙特卡罗结果在一个广泛的参数范围内，覆盖绝缘相和金属绝缘体交叉制度在不太低的温度。作为微扰强耦合杂质解的一个应用，我们研究了哈伯德模型中Mott绝缘相的二重占据对相互作用或跳跃的动力学变化的响应，这种技术已被用作超冷费米子气体中Mott绝缘态的探针。
英文摘要：
We solve the impurity problem which arises within nonequilibrium dynamical mean-field theory for the Hubbard model by means of a self-consistent perturbation expansion around the atomic limit. While the lowest order, known as the non-crossing approximation (NCA), is reliable only when the interaction U is much larger than the bandwidth, low-order corrections to the NCA turn out to be sufficient to reproduce numerically exact Monte Carlo results in a wide parameter range that covers the insulating phase and the metal-insulator crossover regime at not too low temperatures. As an application of the perturbative strong-coupling impurity solver we investigate the response of the double occupancy in the Mott insulating phase of the Hubbard model to a dynamical change of the interaction or the hopping, a technique which has been used as a probe of the Mott insulating state in ultracold fermionic gases.
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