1:30 pm MCP 201
Kekulé Superconductivity in Twisted Magic-Angle Bilayer Graphene.
Since the discovery of superconductivity in twisted magic-angle bilayer graphene, its precise nature has remained an open question. Motivated by recent scanning tunneling microscopy (STM) experiments reporting Kekulé ordering in moiré graphene superconductors, we develop a microscopic theory of superconductivity in twisted bilayer graphene. We identify the superconducting state as an intravalley, finite-momentum pair-density wave (PDW) that intrinsically carries a Kekulé modulation.
In this talk, I will show how this state accounts for four salient experimental features: (i) the spontaneous breaking of C₃ rotational symmetry, leading to nematic order; (ii) spin-triplet pairing; (iii) a quasiparticle density of states that evolves from a V-shaped profile to a fully gapped, U-shaped spectrum as the attractive interaction increases; and (iv) the systematic temperature dependence of the zero-bias conductance. I will further show that, even at modest interaction strength, this state approaches a BEC-like regime, consistent with the extremely short coherence lengths observed experimentally. Finally, I will discuss the geometric electromagnetic response of this Kekulé PDW state, emphasizing its characteristic signatures and their implications for identifying this state as a candidate for unconventional superconductivity.