# Large linear-in-temperature resistivity in twisted bilayer graphene

## Abstract

Twisted bilayer graphene has recently emerged as a platform for hosting correlated phenomena. For twist angles near θ ≈ 1.1°, the low-energy electronic structure of twisted bilayer graphene features isolated bands with a flat dispersion1,2. Recent experiments have observed a variety of low-temperature phases that appear to be driven by electron interactions, including insulating states, superconductivity and magnetism3,4,5,6. Here we report electrical transport measurements up to room temperature for twist angles varying between 0.75° and 2°. We find that the resistivity, ρ, scales linearly with temperature, T, over a wide range of T before falling again owing to interband activation. The T-linear response is much larger than observed in monolayer graphene for all measured devices, and in particular increases by more than three orders of magnitude in the range where the flat band exists. Our results point to the dominant role of electron–phonon scattering in twisted bilayer graphene, with possible implications for the origin of the observed superconductivity.

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## Data availability

The data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request.

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## Acknowledgements

The authors thank S. Das Sarma and F. Wu for sharing their unpublished theoretical results, and acknowledge further discussions with L. Balents and T. Senthil. Work at both Columbia and UCSB was funded by the Army Research Office under award W911NF-17-1-0323. Sample device design and fabrication was partially supported by DoE Pro-QM EFRC (DE-SC0019443). A.F.Y. and C.R.D. separately acknowledge the support of the David and Lucile Packard Foundation. K.W. and T.T. acknowledge support from the Elemental Strategy Initiative conducted by the MEXT, Japan and the CREST (JPMJCR15F3), JST. A portion of this work was carried out at the KITP, Santa Barbara, supported by the National Science Foundation under grant number NSF PHY-1748958.

## Author information

M.Y., S.C., H.P. and Y.Z. fabricated the devices. H.P., M.Y. and S.C. performed the measurements and analysed the data. K.W. and T.T. grew the hexagonal boron nitride crystals. C.R.D. and A.F.Y. advised on the experiments. The manuscript was written with input from all authors.

Correspondence to Cory R. Dean or Andrea F. Young.

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### Competing interests

The authors declare no competing interests.

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## Supplementary information

### Supplementary Information

Supplementary Figs. 1–8 and ref. 1.

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