A new numerical algorithm for the double-orbital Hubbard model -- Hund-coupled pairing symmetry in the doped case

TL;DR

This paper introduces a new numerical transformation that reduces the sign problem in quantum Monte Carlo simulations of the double-orbital Hubbard model, revealing stable Hund-coupled spin-triplet pairing across various band fillings.

Contribution

A real, exact discrete transformation for exchange and pair-hopping interactions that enhances QMC simulations of multi-orbital systems.

Findings

Hund-coupled spin-triplet pairing is stable over a wide doping range.

The transformation suppresses the sign problem in non-half-filled bands.

The method enables detailed study of pairing symmetries in multi-orbital models.

Abstract

In order to numerically study electron correlation effects in multi-orbital systems, we propose a new type of discrete transformation for the exchange (Hund's coupling) and pair-hopping interactions to be used in the dynamical mean field theory + quantum Monte Carlo method. The transformation, which is real and exact, turns out to suppress the sign problem in a wide parameter region including non-half-filled bands. This enables us to obtain the dominant pairing symmetry in the double-orbital Hubbard model, which shows that the spin-triplet, orbital-antisymmetric pairing that exploits Hund's coupling is stable in a wide region of the band filling.