一种新型拓扑安德森绝缘体被发现，其边缘态能抵抗强无序干扰，且可通过加热诱导相变。研究表明，通过引入热量，材料可以从拓扑绝缘体转变为拓扑安德森绝缘体，再到完全绝缘的安德森绝缘体。这一发现为调控材料的拓扑状态和电子传导性提供了非侵入性的新方法，加深了对无序对拓扑相影响的理解。

🧲 拓扑安德森绝缘体具备特殊导电性：这类材料内部绝缘，但其边缘或表面支持电子流动，且这些边缘态能有效抵抗弱无序干扰，展现出优异的鲁棒性。

💡 相变机制由“迁移率间隙”决定：与常规拓扑绝缘体依赖“带隙”不同，拓扑安德森绝缘体的费米能级位于“迁移率间隙”，这使得电子能够存在于此，但处于被局域化的状态，从而保证了边缘态的高度稳定。

🔥 热力诱导相变是关键创新：以往拓扑绝缘体到拓扑安德森绝缘体的转变需要结构改性，而本研究首次证明可通过施加热量来实现这一相变。加热使系统变为非厄米态，从而在不改变材料结构的前提下，提供了一种全新的调控材料拓扑状态的途径。

🌡️ 加热过程中的多重相变：进一步的加热实验揭示了材料的连续相变过程。材料会先从拓扑绝缘体转变为拓扑安德森绝缘体，然后继续加热会引发第二次相变，最终变为安德森绝缘体，此时所有电子态均被局域化，材料完全绝缘，不再有边缘传导。

Topological insulators are materials that behave as insulators in their interior but support the flow of electrons along their edges or surfaces. These edge states are protected against weak disorder, such as impurities, but can be disrupted by strong disorder. Recently, researchers have explored a new class of materials known as topological Anderson insulators. In these systems, strong disorder leads to Anderson localization, which prevents wave propagation in the bulk while still allowing robust edge conduction.

The Fermi energy is the highest energy an electron can have in a material at absolute zero temperature. If the Fermi energy lies in a conductive region, the material will conduct; if it lies in a ‘gap’, the material will be insulating. In a conventional topological insulator, the Fermi energy sits within the band gap. In topological Anderson insulators, it sits within the mobility gap rather than the conventional band gap, making the edge states highly stable. Electrons can exist in the mobility gap (unlike in the band gap), but they are localized and trapped. Until now, the transition from a topological insulator to a topological Anderson insulator has only been achieved through structural modifications, which limits the ability to tune the material’s properties.

In this study, the authors present both theoretical and experimental evidence that this phase transition can be induced by applying heat. Heating introduces energy exchange with the environment, making the system non-Hermitian. This approach provides a new way to control the topological state of a material without altering its structure. Further heating prompts a second phase transition, from a topological Anderson insulator to an Anderson insulator, where all electronic states become localized, and the material becomes fully insulating with no edge conduction.

This research deepens our understanding of how disorder influences topological phases and introduces a novel method for engineering and tuning these phases using thermal effects. It also provides a powerful tool for modulating electron conductivity through a simple, non-invasive technique.

Do you want to learn more about this topic?

Interacting topological insulators: a review by Stephan Rachel (2018)

The post A new path to robust edge states using heat and disorder appeared first on Physics World.