Performance of the coupled cluster singles and doubles method on two-dimensional quantum dots

TL;DR

This paper presents an implementation of the CCSD method for two-dimensional quantum dots, demonstrating its advantages in accuracy and basis set usage compared to other methods, and analyzing the effects of higher excitations.

Contribution

The study introduces an efficient CCSD implementation for 2D quantum dots and compares its accuracy with other high-precision approaches, highlighting its ability to handle large basis sets.

Findings

CCSD provides energy estimates comparable to Quantum Monte Carlo methods.

Large basis sets can be effectively used in CCSD for quantum dots.

Truncating triple excitations introduces errors comparable to other high-accuracy methods.

Abstract

An implementation of the coupled-cluster single- and double excitations (CCSD) method on two-dimensional quantum dots is presented. Advantages and limitations are studied through comparison with other high accuracy approaches for two to eight confined electrons. The possibility to effectively use a very large basis set is found to be an important advantage compared to full configuration interaction implementations. For the two to eight electron ground states, with a confinement strength close to what is used in experiments, the error in the energy introduced by truncating triple excitations and beyond is shown to be on the same level or less than the differences in energy given by two different Quantum Monte Carlo methods. Convergence of the iterative solution of the coupled cluster equations is, for some cases, found for surprisingly weak confinement strengths even when starting from a non-interacting basis. The limit where the missing triple and higher excitations become relevant is investigated through comparison with full Configuration Interaction results.