Identification of superconducting pairing symmetry in twisted bilayer graphene using in-plane magnetic field and strain

Fengcheng Wu; Sankar Das Sarma

doi:10.1103/PhysRevB.99.220507

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Identification of superconducting pairing symmetry in twisted bilayer graphene using in-plane magnetic field and strain

Fengcheng Wu, Sankar Das Sarma

DOI 10.1103/PhysRevB.99.220507 · Physical Review B

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Abstract

We show how the pairing symmetry of superconducting states in twisted bilayer graphene can be experimentally identified by theoretically studying effects of externally applied in-plane magnetic field and strain. In the low-field regime, superconducting critical temperature Tc is suppressed by in-plane magnetic field B∥ in singlet channels, but is enhanced by weak B∥ in triplet channels, providing an important distinction. The in-plane angular dependence of the critical B∥,c has a sixfold rotational symmetry, which is broken when strain is present. We show that anisotropy in B∥,c generated by strain can be similar for s- and d-wave channels in moiré superlattices. The d-wave state is pinned to be nematic by strain and consequently gapless, which is distinguishable from the fully gapped s-wave state by tunneling gap measurements.