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Topological Insulators Excited with Lasers Could Have Massless Electrons

At the University of Tsukuba, researchers have shown that electrons can move as if they did not have any mass when some materials known as “topological insulators” are irradiated using laser beams.

This study could pave the way to a new class of highly effective photonic crystals and electronic devices.

Traditional electronic devices mainly depend on silicon crystals. From the perspective of the electrons that constitute the electrical signals running via these materials, the systems are too large to be practically infinite.

This makes a majority of the electronic structures mimic the mathematical solutions of a “bulk” endless repeating lattice. But latest advances in solid-state physics have indicated the viability of “topological insulators”—materials that generally act as electrical insulators, but include states that occur at the material’s edge.

Such surface states made by the sudden transition from the material to empty space exhibit unique properties, like protection from being interrupted by disorder, which can take place with other electronic states.

In some cases, the electrons can move with such ease that they behave as if they had zero mass. Although topological states are quite interesting, not much is known on how to produce them and how they act.

A team of researchers from the University of Tsukuba has now employed theoretical calculations to forecast the electronic states that can develop when a laser irradiates a topological insulator. This can help bridge gaps in people’s understanding regarding these materials since empirical data is hard to achieve.

Experiments on non-equilibrium topological states remain scarce, even though they have the potential to provide a new platform to create unexpected massless Dirac states.

Ken-ichi Hino, Study Senior Author and Professor, University of Tsukuba

The researchers described that the study results were the outcome of making fourfold accidental degeneracies at the high-symmetry points.

We hope our work will accelerate the process of investigating topological insulators.

Ken-ichi Hino, Study Senior Author and Professor, University of Tsukuba

The findings of this study might lay the basis for new computer systems that lose less energy as waste based on such materials.

Journal Reference

Zhang, B., et al. (2021) Edge states of Floquet–Dirac semimetal in a laser-driven semiconductor quantum-well. Scientific Reports.

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