Many-body phase transitions found in suspended graphene multilayers!

Discovery of graphene—monolayer of graphite—has driven numerous developments in studies on atomically 'thin' 2D crystals where a rich variety of fascinating new phenomena has been observed. On the other hand, it has also provided another interesting research directions by enabling the isolation of arbitrary N-layers with well-preserved structural and electrical integrity. Taking advantage of such possibilities, we have studied transport properties of ultraclean suspended graphene multilayers and found that Bernal-stacked N-layer graphene exhibits finite-temperature phase transitions to many-body insulating states, surprisingly up to N=8 at temperatures as high as 100 K. These findings represent the first unambiguous experimental proof of the finite-temperature phase transitions solely driven by Coulomb interactions in low-dimensional systems, and clearly show that even the graphene layers as thick as N=8 behave quite differently from the graphite, the well-known semimetal with negligible Coulomb interactions effects. We are currently searching for the microscopic origin of the phenomena and the way to control their properties. Stay tuned for more developments coming up next.

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