Quantum spin helices more stable than the ground state: onset of helical protection
Abstract
Topological magnetic structures are promising candidates for resilient information storage. An elementary example are spin helices in one-dimensional easy-plane quantum magnets. To quantify their stability, we numerically implement the stochastic Schr\"odinger equation and time-dependent perturbation theory for spin chains with fluctuating local magnetic fields. We find two classes of quantum spin helices that can reach and even exceed ground-state stability: Spin-current-maximizing helices and, for fine-tuned boundary conditions, the recently discovered "phantom helices". Beyond that, we show that the helicity itself (left- or right-rotating) is even more stable. We explain these findings by separated helical sectors and connect them to topological sectors in continuous spin systems. The resulting helical protection mechanism is a promising phenomenon towards stabilizing helical quantum structures, e.g., in ultracold atoms and solid state systems. We also identify an - up to our knowledge - previously unknown new type of phantom helices.
Keywords
Cite
@article{arxiv.2302.02603,
title = {Quantum spin helices more stable than the ground state: onset of helical protection},
author = {Stefan Kühn and Felix Gerken and Lena Funcke and Tobias Hartung and Paolo Stornati and Karl Jansen and Thore Posske},
journal= {arXiv preprint arXiv:2302.02603},
year = {2023}
}
Comments
6+4 pages, 3 figures; version 2: minor updates, additional references