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

Area of Science:

• Condensed Matter Physics
• Quantum Phase Transitions
• Statistical Mechanics

Background:

• Continuous Quantum Transitions (CQTs) in homogeneous systems are sensitive to perturbations.
• Symmetry-breaking defects, induced by localized fields, can significantly alter system behavior.
• Understanding defect effects is crucial for characterizing quantum critical phenomena.

Purpose of the Study:

• To investigate the impact of symmetry-breaking defects on Continuous Quantum Transitions (CQTs).
• To analyze the emergence of critical crossover regimes driven by these defects.
• To characterize these crossover phenomena using ground-state fidelity and fidelity susceptibility.

Main Methods:

• Renormalization-Group (RG) framework
• Finite-size scaling analysis
• Analysis of ground-state fidelity and fidelity susceptibility in 1D quantum Ising models

Main Results:

• Symmetry-breaking defects induce critical crossover regimes at CQTs.
• Ground-state properties change rapidly within these crossover regimes.
• Fidelity susceptibility exhibits a power-law divergence with system size in the crossover regime, linked to RG defect dimension.

Conclusions:

• Defects play a critical role in modifying quantum critical behavior.
• The observed crossover phenomena are a direct consequence of defect-induced symmetry breaking.
• RG theory and numerical simulations confirm the power-law divergence of fidelity susceptibility, characterizing defect-driven transitions.