Tungsten ditelluride (WTe2) is a transition metal dichalcogenide with numerous advantageous properties and characteristics, which makes it an ideal material for a wide range of electronic applications. Past studies have established that 2D WTe2 crystals arranged in a single layer form the first monolayer topological insulator, exhibiting topological properties that survive up to very high temperatures (~100 K).
Over the past few years, physicists have been able to understand the origin of the material's topology fairly well. Nonetheless, the reasons why WTe2 monolayer behaves as an insulator (i.e., electrons cannot move freely in the material) remain unclear. Theoretical predictions and calculations suggest that the material should in principle be a semimetal, in which electrons and holes coexist and move freely.
Researchers at Princeton University have recently carried out a study investigating the electronic properties of monolayer WTe2, with the hope of better understanding the reasons why it acts as an insulator. Their paper, published in Nature Physics, provides strong evidence that the material is an excitonic insulator, arising from the spontaneous formation of electron-hole bound states known as 'excitons.'
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