Correlated Insulating and Superconducting States in Twisted Bilayer Graphene Below the Magic Angle

Emilio Codecido; Qiyue Wang; Ryan Koester; Shi Che; Haidong Tian; Rui Lv; Son Tran; Kenji Watanabe; Takashi Taniguchi; Fan Zhang; Marc Bockrath; Chun Ning Lau

arXiv · 1902.05151

Correlated Insulating and Superconducting States in Twisted Bilayer Graphene Below the Magic Angle

Emilio Codecido·Qiyue Wang·Ryan Koester·Shi Che·Haidong Tian·Rui Lv·Son Tran·Kenji Watanabe·Takashi Taniguchi·Fan Zhang·Marc Bockrath·Chun Ning Lau

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Abstract

The emergence of flat bands and correlated behaviors in 'magic angle' twisted bilayer graphene (tBLG) has sparked tremendous interest, though many aspects of the system are under intense debate. Here we report observation of both superconductivity and the Mott-like insulating state in a tBLG device with a twist angle of approximately 0.93, which is smaller than the magic angle by 15%. At an electron concentration of +/-5 electrons per moire unit cell, we observe a narrow resistance peak with an activation energy gap of approximately 0.1 meV, indicating the existence of an additional correlated insulating state. This is consistent with theory predicting the presence of a high-energy band with an energetically flat dispersion. At a doping of +/-12 electrons per moire unit cell we observe a resistance peak due to the presence of Dirac points in the spectrum. Our results reveal that the magic range of tBLG is in fact larger than what is previously expected, and provide a wealth of new information to help decipher the strongly correlated phenomena observed in tBLG.

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Emilio Codecido, Qiyue Wang, Ryan Koester, Shi Che, Haidong Tian, Rui Lv, Son Tran, Kenji Watanabe, Takashi Taniguchi, Fan Zhang, Marc Bockrath, Chun Ning Lau. 2019-02-13. Correlated Insulating and Superconducting States in Twisted Bilayer Graphene Below the Magic Angle. https://arxiv.org/abs/1902.05151

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