Combined spontaneous symmetry-breaking and symmetry-protected topological order from cluster charge interaction

Anomalous Spontaneous Symmetry Breaking in non-Hermitian Systems with Biorthogonal Z2-symmetry

Landau's spontaneous symmetry breaking theory is a fundamental theory that describes the collective behaviors in many-body systems. It was well known that for usual spontaneous symmetry breaking in Hermitian systems, the order-disorder phase transition with gap closing and spontaneous symmetry breaking occur at the same critical point. In this paper, we generalized the Landau's spontaneous symmetry breaking theory to the cases in non-Hermitian (NH) many-body systems with biorthogonal Z2 symmetry and tried to discover certain universal features. We were surprised to find that the effect of the …

Dynamical signatures of symmetry protected topology following symmetry breaking

We investigate topological signatures in the short-time non-equilibrium dynamics of symmetry protected topological (SPT) systems starting from initial states which break the protecting symmetry. Naïvely, one might expect that topology loses meaning when a protecting symmetry is broken. Defying this intuition, we illustrate, in an interacting Su-Schrieffer-Heeger (SSH) model, how this combination of symmetry breaking and quench dynamics can give rise to both single-particle and many-body signatures of topology. From the dynamics of the symmetry broken state, we find that we are able to dynamica…

Topological and Error-Correcting Properties for Symmetry-Protected Topological Order

We discuss the symmetry-protected topological (SPT) orders for bosonic systems from an information-theoretic viewpoint. We show that with a proper choice of the onsite basis, the degenerate ground-state space of SPT orders (on a manifold with boundary) is a quantum error-correcting code with macroscopic classical distance, hence is stable against any local bit-flip errors. We show that this error-correcting property of the SPT orders has a natural connection to that of the symmetry-breaking orders, whose degenerate ground-state space is a classical error-correcting code with a macroscopic dist…

Large-radius Holstein polaron and the problem of spontaneous symmetry breaking

A translation-invariant solution is found for a large-radius Holstein polaron whose energy in the strong coupling limit is lower than that obtained by Holstein. The wave function corresponding to this solution is delocalized. A conclusion is made about the absence of a spontaneous symmetry breaking in the quantum system discussed.

强到弱自发对称性破缺与平均对称性保护拓扑序相遇

Strong-to-weak spontaneous symmetry breaking meets average symmetry-protected topological order

本研究结合强到弱自发对称性破缺与平均对称性保护拓扑序，提出开放系统特有的双ASPT新相，通过虚林德布拉德形式体系探究一维Z₂对称系统相图，发现拓扑不同的两个三相点，推动开放系统量子相分类研究。

On the relation between decoherence and spontaneous symmetry breaking

We have recently shown that there is a limit to quantum coherence in many-particle spin qubits due to spontaneous symmetry breaking. These results were derived for the Lieb-Mattis spin model. Here we will show that the underlying mechanism of decoherence in systems with spontaneous symmetry breaking is in fact more general. We present here a generic route to finding the decoherence time associated with spontaneous symmetry breaking in many particle qubits, and subsequently we apply this approach to two model systems, indicating how the continuous symmetries in these models are spontaneously br…

Spontaneous Symmetry Breaking, Spectral Statistics, and the Ramp

Ensembles of quantum chaotic systems are expected to exhibit energy eigenvalues with random-matrix-like level repulsion between pairs of energies separated by less than the inverse Thouless time. Recent research has shown that exact and approximate global symmetries of a system have clear signatures in these spectral statistics, enhancing the spectral form factor or correspondingly weakening level repulsion. This paper extends those results to the case of spontaneous symmetry breaking, and shows that, surprisingly, spontaneously breaking a symmetry further enhances the spectral form factor. Fo…

An intrinsic limit to quantum coherence due to spontaneous symmetry breaking

We investigate the influence of spontaneous symmetry breaking on the decoherence of a many-particle quantum system. This decoherence process is analyzed in an exactly solvable model system that is known to be representative of symmetry broken macroscopic systems in equilibrium. It is shown that spontaneous symmetry breaking imposes a fundamental limit to the time that a system can stay quantum coherent. This universal timescale is $t_{spon} \simeq 2πN \hbar / (k_B T)$, given in terms of the number of microscopic degrees of freedom $N$, temperature $T$, and the constants of Planck ($\hbar$) and…

相互作用马约拉纳链中的自发超对称破缺与南部-戈德斯通模式

Spontaneous Supersymmetry Breaking and Nambu-Goldstone Modes in Interacting Majorana Chains

本文研究相互作用马约拉纳链中的自发超对称破缺，引入具有SUSY的模型并分析其产生的南部-戈德斯通模式，以弥补非相对论系统中该问题研究不足的空白。

通过非厄米构造实现热平衡中的一维自发对称性破缺

1D Spontaneous Symmetry Breaking in thermal equilibrium via Non-Hermitian Construction

本研究通过局部非厄米构造分析一维厄米模型，发现其在有限温度和周期边界条件下可实现自发对称性破缺与长程序，为对称性破缺与非厄米性提供了新颖的自发起源。