Quantum materials

Quantum materials is a broad term to put under the same umbrella materials that present strong electronic correlations and/or some type of electronic order (superconducting, magnetic order),  or materials whose electronic properties are linked to non-generic quantum effects, such as topological insulators, Dirac electron systems such as graphene, as well as systems whose collective properties are governed by genuinely quantum behavior, such as ultra-cold atoms , cold excitons,  polaritons, etc. The label Quantum Materials has a strong overlap with Condensed Matter Physics, although the latter is a broader field of research that encompasses classical, yet non-trivial, phenomena, such as soft condensed matter. A common thread in the study of Quantum Materials is the concept of emergence, as advocated by P. W. Anderson in his famous article More is Different, by David Pines and Robert Laughlin in their article The theory of everything.

In 2012, Joseph Orenstein published an article in Physics Today about Ultrafast Spectroscopy of Quantum Materials. In that paper we can read that

"Quantum materials is a label that has come to signify the area of condensed-matter physics formerly known as strongly correlated electronic systems. Although the field is broad, a unifying theme is the discovery and investigation of materials whose electronic properties cannot be understood with concepts from contemporary condensed-matter textbooks".

As a paradigmatic example, Orenstein refers to the breakdown of Landau Fermi liquid theory due to strong correlations. The use of the term Quantum Materials been extended and applied to other systems, such as topological insulators, and Dirac electron materials. The term has gained momentum since the article The rise of quantum materials by Andrea Taroni was published in Nature Physics in 2016. Quoting Taroni:

on a trivial level all materials exist thanks to the laws of quantum mechanics, and there are cynics who will privately wonder if the description isn't too broad and, well, catchy for its own good. But given the history of condensed-matter physics that we have just outlined, there are good reasons to embrace quantum materials. In essence, they provide a common thread linking disparate communities of researchers working on a variety of problems at the frontiers of physics, materials science and engineering.

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