Multiversality and Unnecessary Criticality in One Dimension

TL;DR

This paper introduces microscopic spin ladder models that display unique critical behaviors, including multiversality and unnecessary criticality, which are analyzed through bosonization and DMRG simulations.

Contribution

It demonstrates the existence of critical surfaces with properties not inferred from neighboring phases, revealing new types of critical phenomena in one-dimensional systems.

Findings

Identification of critical surfaces with novel properties

Evidence of multiversality and unnecessary criticality in spin ladders

Use of bosonization and DMRG to analyze critical behaviors

Abstract

We present microscopic models of spin ladders which exhibit continuous critical surfaces whose properties and existence, unusually, cannot be inferred from those of the flanking phases. These models exhibit either `multiversality' -- the presence of different universality classes over finite regions of a critical surface separating two distinct phases -- or its close cousin, `unnecessary criticality'-- the presence of a stable critical surface within a single, possibly trivial, phase. We elucidate these properties using Abelian bosonization and density-matrix renormalization-group simulations, and attempt to distill the key ingredients required to generalize these considerations.