Anisotropy lifts topological protection of transport in pumped spin chains
Abstract
We investigate the prospect of topological spin pumping and transport in a dimerized spin-1/2 anisotropic XY chain with tunable in-plane anisotropy. Through a Jordan-Wigner transformation, the system maps onto an extended Rice-Mele-type fermionic model whose momentum-space band structure exhibits gapped regions characterized by nonzero Chern numbers (± 1) as well as trivial and gapless regimes. Conventional momentum-space analysis therefore predicts quantized Thouless-type spin pumping in parts of the Chern number diagram. However, real-space time evolution under open boundary conditions reveals that the spin transport is generally not quantized away from the isotropic limit. In the anisotropic regime, eigen-energy states within the transporting subspace hybridize during the driving cycle, leading to a transport that depends on details of the driving protocol. Quantized pumping and transport survive only in the isotropic limit, where the Hamiltonian reduces to decoupled Rice-Mele sectors and the transported spin component is conserved. Our results demonstrate that momentum-space topological invariants alone do not guarantee quantized spin transport in anisotropic spin chains. More broadly, they show that the conventional Thouless-pumping framework does not straightforwardly extend to situations where the transported quantity is not conserved, highlighting the importance of real-space diagnostics in topological transport phenomena.
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BibTeX
@misc{pal2026anisotropy,
title = {{Anisotropy lifts topological protection of transport in pumped spin chains}},
author = {Mainak Pal},
howpublished = {arXiv},
year = {2026},
month = nov,
doi = {10.48550/arxiv.2611.08385},
eprint = {2611.08385},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2611.08385},
}
RIS
TY - UNPB
TI - Anisotropy lifts topological protection of transport in pumped spin chains
AU - Mainak Pal
PY - 2026
DA - 2026/11/05
PB - arXiv
DO - 10.48550/arxiv.2611.08385
UR - https://arxiv.org/abs/2611.08385
AB - We investigate the prospect of topological spin pumping and transport in a dimerized spin-1/2 anisotropic XY chain with tunable in-plane anisotropy. Through a Jordan-Wigner transformation, the system maps onto an extended Rice-Mele-type fermionic model whose momentum-space band structure exhibits gapped regions characterized by nonzero Chern numbers (± 1) as well as trivial and gapless regimes. Conventional momentum-space analysis therefore predicts quantized Thouless-type spin pumping in parts of the Chern number diagram. However, real-space time evolution under open boundary conditions reveals that the spin transport is generally not quantized away from the isotropic limit. In the anisotropic regime, eigen-energy states within the transporting subspace hybridize during the driving cycle, leading to a transport that depends on details of the driving protocol. Quantized pumping and transport survive only in the isotropic limit, where the Hamiltonian reduces to decoupled Rice-Mele sectors and the transported spin component is conserved. Our results demonstrate that momentum-space topological invariants alone do not guarantee quantized spin transport in anisotropic spin chains. More broadly, they show that the conventional Thouless-pumping framework does not straightforwardly extend to situations where the transported quantity is not conserved, highlighting the importance of real-space diagnostics in topological transport phenomena.
ER -