Regardless of the model and platform details, critical phenomena exhibit universal behaviors that are remarkably consistent across various experiments and theories, resulting in a significant scientific success of condensed matter physics. One widely known and commonly used example is the two-dimensional (2D) quantum Hall transition; however, its universal exponents still somewhat conflict between experiments, theoretical models, and numerical ansatzes. We study the critical behaviors of quasi-2D Weyl semimetal systems with a finite thickness $L_z>1$, disorder, and external magnetic field $B_z$. By analyzing the scaling behaviors of the localization lengths and local density of states using recursive methods, we find that the finite thickness yields a deviation from the 2D quantum Hall universality ($L_z=1$ case) and a crossover toward the three-dimensional (3D) Gaussian unitary ensemble ($L_z\to \infty$ limit), potentially offering another cause of the discrepancy. Our work demonstrates the often-overlooked importance of auxiliary degrees of freedom, such as thickness, and that 3D quantum Hall physics is not merely a trivial finite-thickness extension of its 2D counterpart.

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• Anderson localization
• Quantum Hall effect
• Quantum criticality
• Quantum phase transitions
• Topological phase transition
• Topological materials
• Weyl semimetal