Mott-insulator-to-superconductor transition in a two-dimensional superlattice

TL;DR

This paper investigates the quantum phase transition from Mott-insulator to superconductor in a 2D fermionic Hubbard model with a superlattice, revealing universality class and excitation nature through computational methods.

Contribution

It introduces a model suitable for optical lattice experiments and characterizes the transition's universality class and excitation types using quantum Monte Carlo and exact diagonalization.

Findings

Transition belongs to the 3D-XY universality class.

Charge excitations can be fermionic or bosonic.

The model is relevant for optical lattice experiments.

Abstract

We use quantum Monte Carlo and exact diagonalization calculations to study the Mott-insulator to superconductor quantum phase transition in a two-dimensional fermionic Hubbard model with attractive interactions in the presence of a superlattice potential. The model introduced offers unique possibilities to study such transitions in optical lattice experiments. We show that, in regimes with moderate to strong interactions, the transition belongs to the 3D-XY universality class. We also explore the character of the lowest energy charge excitations in the insulating and superconducting phases and show that they can be fermionic or bosonic depending on the parameters chosen.