Critical crossover phenomena driven by symmetry-breaking defects at quantum transitions

• URL: http://arxiv.org/abs/2201.00390v1
• Date: Sun, 2 Jan 2022 18:23:54 GMT
• Title: Critical crossover phenomena driven by symmetry-breaking defects at quantum transitions
• Authors: Alessio Franchi, Davide Rossini, Ettore Vicari
• Abstract summary: We study the effects of symmetry-breaking defects at continuous quantum transitions. The problem is addressed within renormalization-group (RG) and finite-size scaling frameworks.
• Score: 0.0
• License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
• Abstract: 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.

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