Strongly interacting electrons in solid-state systems often display multiple broken symmetries in the ground state. The interplay between different order parameters can give rise to a rich phase diagram. We report on the identification of intertwined phases with broken rotational symmetry in magic-angle twisted bilayer graphene (TBG). Using transverse resistance measurements, we find a strongly anisotropic phase located in a “wedge” above the underdoped region of the superconducting dome. Upon its crossing with the superconducting dome, a reduction of the critical temperature is observed. Furthermore, the superconducting state exhibits an anisotropic response to a direction-dependent in-plane magnetic field, revealing nematic ordering across the entire superconducting dome. These results indicate that nematic fluctuations might play an important role in the low-temperature phases of magic-angle TBG.
Bibliographical noteFunding Information:
This work was supported by the STC Center for Integrated Quantum Materials (NSF grant no. DMR-1231319) for most devices? fabrication, transport measurements, and data analysis (Y.C., D.R.-L.). J.M.P. acknowledges the US Department of Energy (DOE), Office of Basic Energy Sciences (BES), Division of Materials Sciences and Engineering under Award DE-SC0001819 for additional device fabrication. D.R.-L. acknowledges partial support from Fundaci?n Bancaria ?la Caixa? (LCF/BQ/AN15/ 10380011) and from the US Army Research Office (grant no. W911NF-17-S-0001). P.J.-H. acknowledges support from the Gordon and Betty Moore Foundation's EPiQS Initiative through grant GBMF9643 and the National Science Foundation (DMR-1809802). The development of new nanofabrication and characterization techniques enabling this work has been supported by the US DOE Office of Science, BES, under award DE?SC0019300. K.W. and T.T. acknowledge support from the Elemental Strategy Initiative conducted by MEXT, Japan (grant no. JPMXP0112101001), JSPS KAKENHI (grant no. JP20H00354), and CREST (JPMJCR15F3), JST. This work made use of the Materials Research Science and Engineering Center Shared Experimental Facilities supported by the National Science Foundation (DMR-0819762) and of Harvard's Center for Nanoscale Systems, supported by the NSF (ECS-0335765). R.M.F. (phenomenological modeling) acknowledges support by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division, under Award no. DE-SC0020045. N.F.Q.Y. and L.F. (in-plane field modeling) were supported by the US DOE, Office of Science, Office of Basic Energy Sciences (BES), Division of Materials Sciences and Engineering under Award DE-SC0018945;
© 2021 American Association for the Advancement of Science. All rights reserved.