Diagnosing 2D symmetry protected topological states via mixed state anomaly

Fuente: arXiv
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Main Authors: Xu, Chao, Zang, Yunlong, Ma, Yixin, Gu, Yingfei, Jiang, Shenghan
Format: Preprint
Published: 2025
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author Xu, Chao
Zang, Yunlong
Ma, Yixin
Gu, Yingfei
Jiang, Shenghan
author_facet Xu, Chao
Zang, Yunlong
Ma, Yixin
Gu, Yingfei
Jiang, Shenghan
contents Symmetry-protected topological (SPT) phases are short-range entangled quantum states characterized by anomalous edge behavior, a manifestation of the bulk-boundary correspondence for topological phases. Moreover, the Li-Haldane conjecture posits that the entanglement spectrum exhibits the same anomaly as the physical edge spectrum, thereby serving as an entanglement-based fingerprint for identifying topological phases. In this work, we extend the entanglement-based diagnostic tools by demonstrating that the edge anomaly is manifested not only in the entanglement spectrum but also in the reduced density matrix itself, a phenomenon we refer to as the mixed state anomaly. Focusing on the two-dimensional $\mathbb{Z}_2$ SPT phase, we show that this anomaly is subtly encoded in symmetry-twisted mixed states, leading to a topological contribution to the disorder parameter beyond the area law, as well as a spontaneous-symmetry-breaking type long-range order when time reversal symmetry is present.
format Preprint
id arxiv_https___arxiv_org_abs_2506_13096
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Diagnosing 2D symmetry protected topological states via mixed state anomaly
Xu, Chao
Zang, Yunlong
Ma, Yixin
Gu, Yingfei
Jiang, Shenghan
Strongly Correlated Electrons
Quantum Physics
Symmetry-protected topological (SPT) phases are short-range entangled quantum states characterized by anomalous edge behavior, a manifestation of the bulk-boundary correspondence for topological phases. Moreover, the Li-Haldane conjecture posits that the entanglement spectrum exhibits the same anomaly as the physical edge spectrum, thereby serving as an entanglement-based fingerprint for identifying topological phases. In this work, we extend the entanglement-based diagnostic tools by demonstrating that the edge anomaly is manifested not only in the entanglement spectrum but also in the reduced density matrix itself, a phenomenon we refer to as the mixed state anomaly. Focusing on the two-dimensional $\mathbb{Z}_2$ SPT phase, we show that this anomaly is subtly encoded in symmetry-twisted mixed states, leading to a topological contribution to the disorder parameter beyond the area law, as well as a spontaneous-symmetry-breaking type long-range order when time reversal symmetry is present.
title Diagnosing 2D symmetry protected topological states via mixed state anomaly
topic Strongly Correlated Electrons
Quantum Physics
url https://arxiv.org/abs/2506.13096