Synopsis: Glass Materials Could Be Topological Insulators

Topological insulators, so far only identified in materials with an ordered crystal structure, could potentially be found in amorphous materials.
Synopsis figure
A. Agarwala/Indian Institute of Science

Topological insulators are insulating in their interior but conduct electricity on their surface. These unique surface states, which are robust against defects and other imperfections, make these materials potentially useful in quantum computing and other applications. All known topological insulators are crystals, but new theoretical work demonstrates that amorphous materials, such as glasses, could be topological insulators. This result could significantly broaden the search for new topological materials.

Topological insulators are characterized by certain symmetries. For example, many topological insulators are symmetric under time reversal, meaning the electronic wave functions are unaltered by a flip in the time direction. These symmetries are said to “protect” the surface states, which means the system can’t switch to another state without going through a phase transition. Current efforts to locate new topological insulators generally assume the desired symmetries are generated in an ordered lattice structure, but nothing precludes these symmetries from appearing in a noncrystalline material.

Adhip Agarwala and Vijay Shenoy from the Indian Institute of Science in Bangalore have investigated whether topological behavior could emerge in amorphous systems. In their study, they assume a box with a large number of lattice sites arranged randomly. Each site can host electrons in one of several energy levels, and electrons can hop between neighboring sites. The authors tuned parameters, such as the lattice density and the spacing of energy levels, and found that the modeled materials could exhibit symmetry-protected surface currents in certain cases. The results suggest that topological insulators could be made by creating glasses with strong spin-orbit coupling or by randomly placing atoms of other elements inside a normal insulator.

This research is published in Physical Review Letters.

–Michael Schirber

Michael Schirber is a Corresponding Editor for Physics based in Lyon, France.


More Features »


More Announcements »

Subject Areas

Topological Insulators

Previous Synopsis

Quantum Information

Trapping a Rydberg Ion

Read More »

Related Articles

Viewpoint: Topological Insulators Turn a Corner
Condensed Matter Physics

Viewpoint: Topological Insulators Turn a Corner

Theorists have discovered topological insulators that are insulating in their interior and on their surfaces but have conducting channels at corners or along edges. Read More »

Synopsis: Even Flocks are Topological
Soft Matter

Synopsis: Even Flocks are Topological

A flocking model that describes birds and cells exhibits topological features when the moving entities are confined to a curved surface. Read More »

Viewpoint: A Roadmap for a Scalable Topological Quantum Computer
Condensed Matter Physics

Viewpoint: A Roadmap for a Scalable Topological Quantum Computer

A team of experimentalists and theorists proposes a scalable protocol for quantum computation based on topological superconductors. Read More »

More Articles