The arena of quantum materials, wherein quantum aspects assert themselves in behavior and properties, may be unfamiliar territory to many. But as science writer Philip Ball writes in the October issue of MRS Bulletin, all matter, in the end, can be explained by this cutting-edge branch of scientific research, which offers “a playground for finding and exploring new physics” and materials.

When the only way to fully understand how a material behaves is to keep the quantum in view, such materials can be grouped as quantum materials. The U.S. Department of Energy describes quantum materials as “solids with exotic physical properties, arising from the quantum mechanical properties of their constituent electrons that have great scientific and/or technological potential.” With exotic names like topological insulators, Weyl semimetals and spin ices (alongside more familiar terms like superconductors and graphene), Ball describes this collection of quantum materials as a “treasure trove of interesting physics and a potential source of useful substances.”

The band structure of graphene. The valence (blue/green) and conduction (red/yellow) bands touch at points K and K’ in momentum space.

In this thought-provoking article, Ball looks at the evolution of the field that arguably began back in the 1950s with superconductivity, which recognized that the ability of some materials to conduct electricity without resistance is a phenomenon that demands a quantum explanation.

The community of researchers that 20 years ago was grappling with high-temperature superconductivity is today more likely to be pondering topological insulators and Weyl semimetals. While researchers who were focusing in the 1980s on the exotic 2D phenomenon called the quantum Hall effect – an effect in which a voltage across an electrical conductor is created by the influence of a magnetic field on the electron paths – are now finding common cause as different fields converge.

This is not simply a matter of scientists jumping on board the latest bandwagon. Rather, it is a reflection of a common experience in physics, whereby concepts developed to explore one phenomenon turn out to be a subset of more general principles. “Quantum materials reveal that properties once thought to be quirks confined to exotic conditions are in fact a significant feature of the materials universe,” writes Ball.

The challenge now is to turn these ideas into real materials and this can only be done by combining expertise from different fields – including solid-state materials synthesis and crystal growth.

This union of fundamental physics and practical materials science is turning into one of the most vibrant areas of physical science today – with many possibilities for exploring new boundaries of physics, including quantum computers that could achieve computational power far in excess of anything the classical computers of today can achieve.

Ball concludes by stating that research on quantum materials is expanding the materials universe by bringing together diverse fields – showing how common themes govern the properties of matter so that compositions and structures that might be considered “exotic” are in fact, more familiar than they may have seemed.

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