Superconducting Transitions in Flat Band Systems

TL;DR

This paper investigates superconducting transitions in flat band systems, specifically the Lieb lattice, using quantum Monte Carlo simulations to explore charge and pairing correlations beyond established theorems.

Contribution

It extends the understanding of the attractive Hubbard model on the Lieb lattice by analyzing real space correlations with quantum Monte Carlo methods.

Findings

Analyzed charge and pair correlations in the Lieb lattice.

Identified signatures of superconducting transitions.

Provided insights into flat band superconductivity mechanisms.

Abstract

The physics of strongly correlated quantum particles within a flat band was originally explored as a route to itinerant ferromagnetism and, indeed, a celebrated theorem by Lieb rigorously establishes that the ground state of the repulsive Hubbard model on a bipartite lattice with unequal number of sites in each sublattice must have nonzero spin S at half-filling. Recently, there has been interest in Lieb geometries due to the possibility of novel topological insulator, nematic, and Bose-Einstein condensed (BEC) phases. In this paper, we extend the understanding of the attractive Hubbard model on the Lieb lattice by using Determinant Quantum Monte Carlo to study real space charge and pair correlation functions not addressed by the Lieb theorems.