Disorder Stabilizes an Anderson Topological Insulator in the Haldane Model
The presence of disorder is a common factor in quantum materials, and its interaction with topological properties can give rise to states of matter not observed in perfectly ordered systems. A recent study uses the Haldane model as a theoretical platform to reveal that chaos not only shifts the boundaries between phases but acts as a key ingredient to stabilize an exotic phase: the Anderson topological insulator. This finding connects topology, electron localization, and criticality in a unique framework. 🌀
A Topological Map in Real Space
The fundamental tool for this advance is the local Chern marker. This quantity, defined directly in real space, allows characterizing the topology of a system even when strong disorder breaks the lattice periodicity. By applying this marker, researchers were able to precisely map the complete phase diagram as a function of energy and disorder strength.
Key Findings from the Mapping:- Disorder does not simply destroy topology but can induce it in certain regimes.
- The Anderson topological insulator phase emerges as a finite and stable domain within the diagram.
- This domain is clearly bounded by regions corresponding to trivial insulators and conventional Anderson insulators.
Sometimes, to achieve order, you first have to add a bit of chaos. Topological physics seems to follow this maxim, where introducing controlled disorder can create a new state of matter.
Universality in Criticality
Upon examining the boundary between different phases, the multifractal analysis of low-energy eigenstates revealed universal behavior. The critical spectra obtained are independent of whether disorder is generating or destroying the system's topological character.
Implications of Universality:- Provides a clear and universal reference for identifying phase transitions in disordered systems.
- Helps diagnose topological phases in real materials, where disorder is always present.
- Places apparently distinct phenomena such as topology, Anderson localization, and quantum criticality under the same theoretical umbrella.
Implications for Materials Research
This work demonstrates that disorder, far from being just a nuisance, can be a resource for designing and stabilizing new topological phases of matter. The use of the local Chern marker as a probe in real space opens a powerful path to explore and verify topology in strongly disordered or non-periodic systems, bringing theory closer to real experimental conditions. The discovery of the Anderson topological insulator in the Haldane model consolidates the idea that chaos and order can cooperate to reveal new fundamental patterns in nature. 🔬