Quantum Phase Transitions in s=1/2 Ising Chain in a Regularly Alternating Transverse Field

TL;DR

This paper investigates the ground-state quantum phase transitions in a periodically modulated s=1/2 Ising chain in a transverse field, revealing how modulation affects the number, position, and nature of critical points.

Contribution

It provides new insights into how regular alternation in the transverse field influences quantum critical behavior and identifies potential new universality classes.

Findings

Number and position of phase transitions depend on field modulation

Most critical behavior matches the uniform chain's universality class

Possible emergence of new critical behavior

Abstract

We consider the ground-state properties of the s=1/2 Ising chain in a transverse field which varies regularly along the chain having a period of alternation 2. Such a model, similarly to its uniform counterpart, exhibits quantum phase transitions. However, the number and the position of the quantum phase transition points depend on the strength of transverse field modulation. The behaviour in the vicinity of the critical field in most cases remains the same as for the uniform chain (i.e. belongs to the square-lattice Ising model universality class). However, a new critical behaviour may also arise. We report the results for critical exponents obtained partially analytically and partially numerically for very long chains consisting of a few thousand sites.