Nodal pair-density-waves from quarter-metal in crystalline graphene multilayers

Abstract: Crystalline graphene heterostructures, namely Bernal bilayer and rhombohedral trilayer graphene, subject to electric displacement fields, display a rich confluence of competing orders, resulting in a valley-degenerate, spin-polarized half-metal at moderate doping, and a spin- and valley-polarized quarter-metal at low doping. Here we show that the annular Fermi surface of such a quarter-metal can be susceptible toward the nucleation of a unique spin and valley polarized superconducting state, accommodating interlayer Cooper pairs that break the translational symmetry, giving rise to a Kekul\'e or columnar pair-density-wave. The superconducting ground state produces isolated Fermi pockets of neutral Majorana fermions, featuring a three-fold rotational symmetry, resulting in power-law scaling physical observables with temperature ($T$), such as specific heat $C_v \sim T$.