Selenium atoms

Major advance in study of quantum materials

Quantum materials
Condensed Matter Physics

In 2016, Professor J.C. Séamus Davis launched a new sub-field in the study of quantum materials following his discovery of an elusive state of quantum matter in the cuprates – copper oxide superconductors. The next step? To see whether this was a unique phenomenon in the cuprates or a ubiquitous and important property of nature.

Radical new technology

Using an improved version of the radically new quantum microscope technology he developed for this purpose, Professor Davis and his group have now found the same exotic state of quantum matter in a widely used and conventional type of material, the transition metal dichalcogenides (TMD).

The findings are published in the paper, “Discovery of a Cooper-pair density wave state in a transition-metal dichalcogenide,” published 25 June in Science. Cooper-pair density waves (PDW) are a form of exotic quantum matter in which pairs of electrons, instead of forming a conventional “superconductor” where all are in the same freely moving state, freeze into an electron-pair crystal aka a pair density wave state (PDW).

Exciting discovery

‘Seeing that PDWs exist in standard materials like TMDs is an exciting discovery,’ comments Professor Davis. ‘TMDs are relatively conventional materials that provide a rich platform for new physics and new technology.  Because our microscopes are extremely sensitive to vibrational and acoustic noise, they are operated remotely in ultra-low vibration laboratories and without the physical presence of human researchers. Thus, pandemic laboratory shutdowns did not terminate these experiments which, moreover, could be directed remotely from Oxford. A year-long campaign of experiments during 2020 resulted in the discovery that electron-pair crystals exist in TMDs. This reveals the ubiquity of this extraordinary state of quantum matter and it greatly enhances future opportunities to study and understand it, in a wide variety of materials.'

Professor Davis also holds professorships at Cornell University and University College Cork.

Discovery of a Cooper-pair density wave state in a transition-metal dichalcogenide, Liu et al, Science, 25 June 2021