String Order in Quench Dynamics as a Probe of Quantum Phase Transitions
Abstract
We study the anisotropic XY chain in a transverse field by introducing a global string order parameter and examining its equilibrium behavior and its quench dynamics from a fully polarized initial state. The corresponding string operator is defined as the product of local projected spin operators over the entire chain. The nonequilibrium order parameter is the long-time average of the logarithm of the string-operator expectation value per site after the quench. For the ground state, its field derivative is singular on the Ising critical lines; after the quench, the steady-state response also records the field boundaries and the anisotropy transition. We derive analytically the nonanalytic behavior of the order parameter at the quantum critical lines. Our results reveal a hidden nonlocal order underlying this paradigmatic model of conventional quantum phase transitions. They also connect measurable spin populations with equilibrium and dynamical topological structure.
Related
- Reply to Comment on "Scaling and universality at noisy quench dynamical quantum phase transitions"
- Statistics as a local phase: crystalline order and quench dynamics of emergent dimers in Ising gauge theories
- Resource Assessment of Classical and Quantum Hardware for Post-Quench Dynamics
- Small-quench Loschmidt dynamics near quantum critical points
- Topological signatures in the quench dynamics of periodically driven quantum systems
BibTeX
@misc{zhang2026string,
title = {{String Order in Quench Dynamics as a Probe of Quantum Phase Transitions}},
author = {H. P. Zhang and Z. Song},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.30647},
eprint = {2610.30647},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.30647},
}
RIS
TY - UNPB
TI - String Order in Quench Dynamics as a Probe of Quantum Phase Transitions
AU - H. P. Zhang
AU - Z. Song
PY - 2026
DA - 2026/10/26
PB - arXiv
DO - 10.48550/arxiv.2610.30647
UR - https://arxiv.org/abs/2610.30647
AB - We study the anisotropic XY chain in a transverse field by introducing a global string order parameter and examining its equilibrium behavior and its quench dynamics from a fully polarized initial state. The corresponding string operator is defined as the product of local projected spin operators over the entire chain. The nonequilibrium order parameter is the long-time average of the logarithm of the string-operator expectation value per site after the quench. For the ground state, its field derivative is singular on the Ising critical lines; after the quench, the steady-state response also records the field boundaries and the anisotropy transition. We derive analytically the nonanalytic behavior of the order parameter at the quantum critical lines. Our results reveal a hidden nonlocal order underlying this paradigmatic model of conventional quantum phase transitions. They also connect measurable spin populations with equilibrium and dynamical topological structure.
ER -