Anderson critical metal phase in trivial states protected by average magnetic crystalline symmetry

TL;DR

The paper discovers a new delocalized metal phase that appears during transitions between trivial insulators, defying typical localization behavior.

Contribution

A new delocalization mechanism is identified in topologically trivial obstructed insulators under certain disorder conditions.

Findings

Intermediate metals become a scale-invariant critical metal phase under quenched disorder respecting magnetic crystalline symmetries.

CMP is explained through a semi-classical percolation problem, not conventional theories like weak anti-localization.

Systematic classification of OAI transitions under various magnetic symmetry groups is provided.

Abstract

Transitions between distinct obstructed atomic insulators (OAIs) protected by crystalline symmetries, where electrons form molecular orbitals centering away from the atom positions, must go through an intermediate metallic phase. In this work, we find that the intermediate metals will become a scale-invariant critical metal phase (CMP) under certain types of quenched disorder that respect the magnetic crystalline symmetries on average. We explicitly construct models respecting average C2zT, m, and C4zT and show their scale-invariance under chemical potential disorder by the finite-size scaling method. Conventional theories, such as weak anti-localization and topological phase transition, cannot explain the underlying mechanism. A quantitative mapping between lattice and network models shows that the CMP can be understood through a semi-classical percolation problem. Ultimately, we systematically classify all the OAI transitions protected by (magnetic) groups \documentclass[12pt]{minimal}
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The authors identify a novel delocalization mechanism for topologically trivial obstructed insulators. In transitioning from two topologically trivial states, where one would expect Anderson’s localization to take place, a delocalized ‘critical metal phase’ appears.

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