Quantum transitions driven by one-bond defects in quantum Ising rings

TL;DR

This paper studies how a bond defect in quantum Ising rings causes a quantum transition between different phases, revealing universal scaling behaviors and implications for nonequilibrium dynamics.

Contribution

It introduces a detailed analysis of defect-driven quantum transitions in Ising rings, including analytical and numerical characterization of scaling functions.

Findings

Identification of a quantum transition driven by a bond defect

Universal scaling functions for gap, susceptibility, and correlations

Implications for nonequilibrium dynamics across the transition

Abstract

We investigate quantum scaling phenomena driven by lower-dimensional defects in quantum Ising-like models. We consider quantum Ising rings in the presence of a bond defect. In the ordered phase, the system undergoes a quantum transition driven by the bond defect between a magnet phase, in which the gap decreases exponentially with increasing size, and a kink phase, in which the gap decreases instead with a power of the size. Close to the transition, the system shows a universal scaling behavior, which we characterize by computing, either analytically or numerically, scaling functions for the gap, the susceptibility, and the two-point correlation function. We discuss the implications of these results for the nonequilibrium dynamics in the presence of a slowly-varying parallel magnetic field h, when going across the first-order quantum transition at h=0.