# Solvable lattice models for metals with Z2 topological order

## TL;DR

This paper introduces two-dimensional quantum dimer models that exhibit metallic states with Z2 topological order, providing insights into unconventional metallic behavior in doped Mott insulators and potential relevance to twisted bilayer graphene.

## Contribution

It constructs exact ground states of generalized dimer models showing fractionalized Fermi liquids with Z2 topological order, extending previous models to describe metallic states with modified Luttinger counts.

## Key findings

- Ground states are fractionalized Fermi liquids with Z2 topological order.
- The Fermi surface volume is proportional to doped hole density, not total electron density.
- Potential applications to magic-angle twisted bilayer graphene.

## Abstract

We present quantum dimer models in two dimensions which realize metallic ground states with Z2 topological order. Our models are generalizations of a dimer model introduced in [PNAS 112,9552-9557 (2015)] to provide an effective description of unconventional metallic states in hole-doped Mott insulators. We construct exact ground state wave functions in a specific parameter regime and show that the ground state realizes a fractionalized Fermi liquid. Due to the presence of Z2 topological order the Luttinger count is modified and the volume enclosed by the Fermi surface is proportional to the density of doped holes away from half filling. We also comment on possible applications to magic-angle twisted bilayer graphene.