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

(submitted), (2021)

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

Tao Yu, Dante M. Kennes, Angel Rubio, Michael A. Sentef

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(2θ B ) , with θ B 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.

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TY and MAS acknowledge nancial support by Deutsche Forschungsgemeinschaft through the Emmy Noether program (SE 2558/2). DMK acknowledges support by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) via RTG 1995, within the Priority Program SPP 2244 \2DMP" and Germany's Excellence Strategy - Cluster of Excellence Matter and Light for Quantum Computing (ML4Q) EXC 2004/1 - 390534769. AR acknowledges support from the European Research Council (ERC- 2015-AdG-694097), UPV/EHU Grupos Consolidados (IT1249-19) and the Cluster of Excellence `CUI: Advanced Imaging of Matter' of the Deutsche Forschungsgemeinschaft (DFG) - EXC 2056 - project ID 390715994. The Flatiron Institute is a division of the Simons Foundation. We acknowledge support from the Max Planck-New York City Center for Non- Equilibrium Quantum Phenomena.

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