Strange correlators for topological quantum systems from bulk-boundary correspondence

TL;DR

This paper develops a systematic method for choosing operators in strange correlators to effectively detect topological phases, relating their decay to edge mode properties and extending applicability to disordered and long-range systems.

Contribution

It introduces a procedure based on bulk-boundary correspondence for selecting operators in strange correlators, improving topological phase detection across various models.

Findings

Relates decay exponents of strange correlators to edge mode scaling dimensions.

Reduces finite-size effects by integrating the moduli of correlators.

Extends strange correlator applicability to disordered and long-range systems.

Abstract

"Strange" correlators provide a tool to detect topological phases arising in many-body models by computing the matrix elements of suitably defined two-point correlations between the states under investigation and trivial reference states. Their effectiveness depends on the choice of the adopted operators. In this paper we give a systematic procedure for this choice, discussing the advantages of choosing operators using the bulk-boundary correspondence of the systems under scrutiny. Via the scaling exponents, we directly relate the algebraic decay of the strange correlators with the scaling dimensions of gapless edge modes operators. We begin our analysis with lattice models hosting symmetry-protected topological phases and we analyze the sums of the strange correlators, pointing out that integrating their moduli substantially reduces cancellations and finite-size effects. We also analyze instances of systems hosting intrinsic topological order, as well as strange correlators between states with different nontrivial topologies. Our results for both translational and non-translational invariant cases, and in presence of on-site disorder and long-range couplings, extend the validity of the strange correlators approach for the diagnosis of topological phases of matter, and indicate a general procedure for their optimal choice.