Free fermion description of a paramagnetic Mott insulator

TL;DR

This paper introduces a novel scheme to describe paramagnetic Mott insulators using free fermions by employing a non-linear transformation and variational approximation, providing a new analytical approach.

Contribution

It presents a new method to model paramagnetic Mott insulators as free fermions through a non-linear transformation involving Majorana fermions, with a variational approximation.

Findings

Provides an upper bound on ground state energy.

Enables free fermion description of Mott insulators.

Applicable at zero and finite temperatures.

Abstract

A scheme is presented that enables a description of a paramagnetic Mott insulator in terms of free fermions. The main idea is to view the physical fermions as a part of a multi-band system and to allow for a correlation between the physical fermions and the auxiliary ones. Technically this is implemented through a non-linear canonical transformation, which is conveniently formulated in terms of Majorana fermions. The transformed Hamiltonian is in the next stage approximated with a free fermion theory. The approximation step is variational and provides an upper bound on the ground state energy at zero or the Free energy at finite temperature.