The Fractional Quantum Hall Effect on a Lattice

TL;DR

This paper investigates the fractional quantum Hall effect on a lattice, demonstrating the existence of incompressible states at certain filling fractions and showing that lattice effects can closely mimic continuum Landau levels, revealing new hierarchical relations.

Contribution

It introduces lattice versions of Landau levels derived from the Hofstadter butterfly and shows they reproduce continuum states with high accuracy, revealing new hierarchical relations.

Findings

Incompressible states at filling fractions ν=1/3, 2/5, 3/7

Lattice states closely match continuum Laughlin states at certain parameters

Hierarchy of states linked to Hofstadter butterfly structure

Abstract

Starting from the Hofstadter butterfly, we define lattice versions of Landau levels as well as a continuum limit which ensures that they scale to continuum Landau levels. By including a next-neighbor repulsive interaction and projecting onto the lowest lattice Landau level, we show that incompressible ground states exist at filling fractions, $\nu = 1/3, 2/5 $ and $3/7$. Already for values of $l_0/a \sim 2$ where $l_0$ ($a$) is the magnetic length (lattice constant), the lattice version of the $\nu = 1/3$ state reproduces with nearly perfect accuracy the the continuum Laughlin state. The numerical data strongly suggests that at odd filling fractions of the lowest lattice Landau level, the lattice constant is an irrelevant length scale. We find a new relation between the hierarchy of incompressible states and the self-similar structure of the Hofstadter butterfly.