Prerequisites for relevant spectral density and convergence of reduced density matrices at low temperatures

Abstract

Hierarchical equations of motion approach with the Drude-Lorentz spectral density has been widely employed in investigating quantum dissipative phenomena. However, it is often computationally costly for low-temperature systems because a number of Matsubara frequencies are involved. In this note, we examine a prerequisite required for spectral density, and demonstrate that relevant spectral density may significantly reduce the number of Matsubara terms to obtain convergent results for low temperatures.

7 pages, 1 figure, 2 tables; J. Phys. Soc. Jpn. 89, xxxxxx (2020)