Stacked quantum Ising systems and quantum Ashkin-Teller model
Abstract
We analyze the quantum states of an isolated composite system consisting of two stacked quantum Ising (SQI) subsystems, coupled by a local Hamiltonian term that preserves the symmetry of each subsystem. The coupling strength is controlled by an intercoupling parameter , with corresponding to decoupled quantum Ising systems. We focus on the quantum correlations of one of the two SQI subsystems, , in the ground state of the global system, and study their dependence on both the state of the weakly-coupled complementary part and the intercoupling strength. We concentrate on regimes in which develops critical long-range correlations. The most interesting physical scenario arises when both SQI subsystems are critical. In particular, for identical SQI subsystems, the global system is equivalent to the quantum Ashkin-Teller model, characterized by an additional interchange symmetry between the two subsystem operators. In this limit, one-dimensional SQI systems exhibit a peculiar critical line along which the length-scale critical exponent varies continuously with , while two-dimensional systems develop quantum multicritical behaviors characterized by an effective enlargement of the symmetry of the critical modes, from the actual symmetry to a continuous O(2) symmetry.
Cite
@article{arxiv.2601.18922,
title = {Stacked quantum Ising systems and quantum Ashkin-Teller model},
author = {Davide Rossini and Ettore Vicari},
journal= {arXiv preprint arXiv:2601.18922},
year = {2026}
}
Comments
16 pages