Nematicity Arising from a Chiral Superconducting Ground State in Magic-Angle Twisted Bilayer Graphene under In-Plane Magnetic Fields


Recent measurements of the resistivity in magic-angle twisted bilayer graphene near the superconducting transition temperature show two-fold anisotropy or nematicity when changing the direction of an in-plane magnetic field [Cao \textit{et al.}, arXiv:2004.04148]. This was interpreted as strong evidence for exotic nematic superconductivity instead of the widely proposed chiral superconductivity. Counter-intuitively, we demonstrate that in two-dimensional chiral superconductors the in-plane magnetic field can hybridize the two chiral superconducting order parameters to induce a phase that shows nematicity in the transport response. Its paraconductivity is modulated as cos(2θB), with θB being the direction of the in-plane magnetic field, consistent with experiment in twisted bilayer graphene. We therefore suggest that, surprisingly, the nematic response reported by Cao \textit{et al.} could provide experimental support for, instead of ruling out, a chiral superconducting state.

Phys. Rev. Lett. 127, 127001 (2021)

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Tao Yu
Tao Yu
Professor, Group Leader

My research interests include Magnetism, Spintronics, Unconventional superconductivity, Quantum transport in low dimensional electronics, and Strong light-matter interaction.