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Superconductivity in Twisted Trilayer Graphene

Mar 20, 2018

Layers of two-dimensional materials stacked with a small twist angle give rise to beating periodic patterns on a scale much larger than the original lattice, referred to as a ‘moiresuperlattice’. Superconductivity and correlated insulator states in magic angle alternatively twisted trilayer graphene (MA-tTG)1 (Fig., top) and ‘moire of moire’ twisted trilayer graphene (MM-tTG)2 (Fig., bottom) have now been experimentally demonstrated.  Initially a van der Waals heterostructure was constructed that consisted of three graphene layers stacked with alternating twist angles. At a theoretically predicted ‘magic angle’ of -1.56° flat electron bands formed with displacement field-tunable superconductivity observed with a maximum critical temperature of 2.1 K.1  Subsequently, a twisted trilayer graphene system with two independently controlled twist angles was fabricated. Correlated insulating states were found near the half filling of the MM-tTG superlattice at an extremely low carrier density, near which was observed a zero-resistance transport behavior at 3.4 K typical of a 2D superconductor.2Together, these findings provide deep understanding of moiré correlated states and unusual superconductivity, which could be utilized for quantum information processing computing platforms.

Authors

P. Kim, E. Kaxiras (Harvard) M. Luskin, K. Wang (U. Minnesota)

Additional Materials

U.S. National Science Foundation and NSF DMREF, Materials for Our Future

This material is based upon work supported by the U.S. National Science Foundation Award No. 2015237. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the U.S. National Science Foundation. This site is maintained collaboratively by principal investigators with NSF DMREF awards, independent of the NSF.