Anderson Transition and Mobility Edges in a Family of 3D Fractal Lattices

TL;DR

This study introduces a family of 3D fractal lattices with tunable spectral dimension to explore Anderson localization and the transition's universality class across noninteger dimensions.

Contribution

The paper presents a controlled fractal lattice platform to systematically study the Anderson transition and mobility edges in noninteger dimensions, revealing the influence of spectral dimension.

Findings

Critical disorder strength increases from 0 to 16.6 as spectral dimension rises from 2 to 3.

Critical exponent approximately inversely proportional to spectral dimension.

Spectral dimension mainly determines the universality class of the transition.

Abstract

Anderson localization is fundamentally controlled by dimensionality, yet the nature of the Anderson transition in continuously tunable noninteger dimensions remains largely unexplored. Here, we introduce a family of three-dimensional fractal lattices with continuously tunable spectral dimension $d_s\in[2,3]$, providing a controlled platform for studying localization physics beyond integer dimensions and across the lower critical dimension $d_s=2$. Using large-scale finite-size scaling analysis, we systematically investigate the Anderson transition and identify mobility edges throughout the fractal family. The critical disorder strength evolves continuously from $0$ to $16.6$ as the spectral dimension increases from $2$ to $3$. We show that the spectral dimension predominantly governs the universality class of the transition, while the precise critical point is additionally influenced by microscopic geometric details of the underlying fractal lattice. The critical exponent exhibits an approximate inverse dependence on $d_s$, providing quantitative insight into scaling theory in noninteger dimensions. Our results establish tunable fractal lattices as a versatile framework for exploring localization and quantum critical phenomena beyond conventional integer-dimensional systems.