Quantum-number projection in the path-integral renormalization group method

TL;DR

This paper introduces a quantum-number projection technique integrated with the path-integral renormalization group method, significantly improving the accuracy and capability to handle excited states in Hubbard model simulations.

Contribution

It develops a novel projection technique combined with the PIRG method, enabling exact symmetry treatment and enhanced numerical efficiency for Hubbard models.

Findings

Enhanced numerical accuracy in Hubbard model calculations.

Ability to handle excited states beyond the ground state.

Effective treatment of spin, momentum, and other symmetries.

Abstract

We present a quantum-number projection technique which enables us to exactly treat spin, momentum and other symmetries embedded in the Hubbard model. By combining this projection technique, we extend the path-integral renormalization group method to improve the efficiency of numerical computations. By taking numerical calculations for the standard Hubbard model and the Hubbard model with next nearest neighbor transfer, we show that the present extended method can extremely enhance numerical accuracy and that it can handle excited states, in addition to the ground state.