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While astrophysicists scan our universe for planets, stars, asteroids and other cosmic objects, material physicists examine the universe of matter. Their quest: to find new materials that could have an application or use, for example, in the development of new computers.

Jeffrey Quilliam, a professor in the Department of Physics at the Université de Sherbrooke, has set his sights on exotic materials, i.e. any substance that is not made up of the same particles as ordinary matter. This is a theoretical concept, as exotic particles are not tangible, making them difficult to investigate.

Lately, the researcher has been exploring Weyl semimetals, a new class of quantum materials that have the physical appearance of metals but are poor conductors of electricity, and whose properties do not change when they are deformed. For example, they retain their properties when stretched or when other materials are added to them.

The researcher is particularly interested in an electromagnetic characteristic of these semimetal called a “chiral anomaly”. When a magnetic field is applied to a Weyl semimetal at a certain angle, its resistance drops and its conductivity increases. This characteristic makes this class of materials interesting for the development of sensors, among other things. The chiral anomaly has been measured by numerous research teams around the world, but the results have recently been called into question.

Jeffrey Quilliam and his collaborators at the Université de Sherbrooke, Ion Garate and André-Marie Tremblay, have developed a different approach for measuring this electromagnetic effect: they use sound waves. By measuring the speed of sound as it passes through the material, they obtained fewer false results (imperfect measurements). They also observed that the electromagnetic effect of Weyl semimetals is weaker than previous research had suggested.

Their original approach is easy to reproduce and could be used to investigate the electrical properties of different materials. For example, it could help physicists discover new particles useful in the quantum field.

The research of Jeffrey Quilliam and his colleagues is a further step towards a fundamental understanding of the quantum physics inside semiconductors, without which today’s computers would not exist.

References:

Field-angle dependence of sound velocity in the Weyl semimetal TaAsInfluence of Landau levels on the phonon dispersion of Weyl semimetalsTopological Materials: Weyl Semimetals