Emergence of Gauss' Law in a $Z_2$ Lattice Gauge Theory

Abstract

We explore a $Z_2$ Hamiltonian lattice gauge theory in one spatial dimension with a coupling $h$, without imposing any Gauss' law constraint. We show that in our model $h=0$ is a free deconfined quantum critical point containing massless fermions where all Gauss' law sectors are equivalent. The coupling $h$ is a relevant perturbation of this critical point and fermions become massive due to confinement and chiral symmetry breaking. To study the emergent Gauss' law sectors at low temperatures in this massive phase we use a quantum Monte Carlo method that samples configurations of the partition function written in a basis in which local conserved charges are diagonal. We find that two Gauss' law sectors, related by particle-hole symmetry, emerge naturally. When the system is doped with an extra particle, many more Gauss's law sectors related by translation invariance emerge. Using results in the range $0.01<h\le 0.15$ we find that three different mass scales of the model behave like $h^p$ where $p\approx 0.579$.

Comments: 7 pages, 8 figures