Quantum Monte Carlo pair orbital wave functions for periodic systems towards the thermodynamical limit: ground states, excitations and spinors

TL;DR

This paper introduces a new quantum Monte Carlo wave function formalism for periodic systems, enabling accurate modeling of ground states, excitations, and spinor interactions near the thermodynamic limit.

Contribution

It develops a novel ab initio wave function approach with explicit Brillouin zone integration, extending to spin-dependent interactions and complex Fermi surfaces.

Findings

Wave functions are BCS-like determinants and pfaffians for various states.

Applicable to quasi-particle band gaps and optical excitations.

Generalizes to spinor pairs for spin-dependent interactions.

Abstract

We derive many-body single- and multi-reference wave functions for quantum Monte Carlo of periodic systems with an anti-symmetric portion that explicitly integrates over the Brillouin zone of one-particle Bloch states. The wave functions are BCS-like determinants for singlets and pfaffians for polarized states built with appropriate pair orbitals. This ab initio formalism is broadly applicable, eg, to description of quasi-particle band gaps, optical excitations and to systems with complicated Fermi surfaces. It generalizes to spin-dependent interactions using two-component spinor pairs.