论文标题
量子过渡时由对称性缺陷驱动的关键跨界现象
Critical crossover phenomena driven by symmetry-breaking defects at quantum transitions
论文作者
论文摘要
我们研究了连续量子转变（CQT）处的对称性缺陷的影响，这可能是由与订单参数运算符耦合的局部外部场产生的。该问题在重归其化组（RG）和有限尺寸的缩放框架中解决。在存在破坏全局$ {\ mathbb z} _2 $对称性的缺陷的情况下，我们考虑了其CQT处的范式一维量子iSing模型。我们表明，这种缺陷会引起显着的关键交叉状态，在这种缺陷中，地面特性经历了从对称条件到对称性的边界的实质性和快速变化。通过分析与缺陷强度的较小变化相关的地面保真度，可以实现由缺陷驱动的这些跨界现象的有效表征。在关键的交叉状态中，忠诚度易感性在增加系统大小时显示出与缺陷强度的RG维度有关的幂律差异；相反，在关键的缺陷制度之外，它仍然是有限的。我们支持带有数值结果的RG缩放参数。
We study the effects of symmetry-breaking defects at continuous quantum transitions (CQTs), which may arise from localized external fields coupled to the order-parameter operator. The problem is addressed within renormalization-group (RG) and finite-size scaling frameworks. We consider the paradigmatic one-dimensional quantum Ising models at their CQT, in the presence of defects which break the global ${\mathbb Z}_2$ symmetry. We show that such defects can give rise to notable critical crossover regimes where the ground-state properties experience substantial and rapid changes, from symmetric conditions to symmetry-breaking boundaries. An effective characterization of these crossover phenomena driven by defects is achieved by analyzing the ground-state fidelity associated with small changes of the defect strength. Within the critical crossover regime, the fidelity susceptibility shows a power-law divergence when increasing the system size, related to the RG dimension of the defect strength; in contrast, outside the critical defect regime, it remains finite. We support the RG scaling arguments with numerical results.
