Efficient approaches in DMFT for multi-degree-of-freedom systems

Although several impurity solvers in DMFT[1] have been proposed, especially in multi-degree-of-freedom systems, there are practical difficulties arising from a trade-off between numerical costs and reliability. In this study, we re-interpret the iterative perturbation theory(IPT)[2] from the perspective of the frequency dependence, and extend it such that costs and reliability can be compatible. From the same perspective, we also develop the methods in which the dual fermion calculation[3] can be performed efficiently and can be combined with any impurity solver. We validate these methods by comparing them with several numerically exact methods. As a result, we confirm that the results of our methods show good agreements with that of the exact methods not only in single-degree-of-freedom systems but also in multi-degree-of-freedom systems. In the presentation, we explain the details of the methods, and show the results of benchmarks.

Reference
[1] A. Georges, et al.: Rev. Mod. Phys. 68 (1996)13.
[2] H. Kajueter et al.: Phys. Rev. Lett. 77 (1996) 131.
[3] A. N. Rubtsov et al.: Phys. Rev. B 77 (2008) 033101.