Junctions and superconducting symmetry in twisted bilayer graphene
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Junctions and superconducting symmetry in twisted bilayer graphene
Héctor Sainz-Cruz, Pierre A. Pantaleón, Vo Tien Phong, Alejandro Jimeno-Pozo, Francisco Guinea
AbstractJunctions provide a wealth of information on the symmetry of the order parameter of superconductors. We analyze junctions between a scanning tunneling microscope (STM) tip and superconducting twisted bilayer graphene (TBG) and TBG Josephson junctions (JJs). We compare superconducting phases that are even or odd under valley exchange (s- or f-wave). The critical current in mixed (s- and f-) JJs strongly depends on the angle between the junction and the lattice. In STM-TBG junctions, due to Andreev reflection, f-wave leads to a prominent peak in subgap conductance, as seen in experiments.
2 comments
scicastboard
Thank you for posting your work.
Question from ScienceCast moderators (CM team):
Usually, the symmetry of the order parameter is defined relative to the symmetry of the underlying lattice, and more specifically according to representations of the discrete symmetry group. In twisted bilayer graphene, the symmetry is very low, how do you define the symmetry of the gap (according to the moire lattice or the underlying honeycomb lattice or something else)?
Question from ScienceCast moderators (CM team):
Usually, the symmetry of the order parameter is defined relative to the symmetry of the underlying lattice, and more specifically according to representations of the discrete symmetry group. In twisted bilayer graphene, the symmetry is very low, how do you define the symmetry of the gap (according to the moire lattice or the underlying honeycomb lattice or something else)?
Héctor Sainz-Cruz
Thank you for the question.
We do a tight-binding model, so the symmetry of the order parameter is realized with microscopic Haldane-like hoppings on the underlying honeycomb lattice.
We do a tight-binding model, so the symmetry of the order parameter is realized with microscopic Haldane-like hoppings on the underlying honeycomb lattice.