Engineering kekule superconductivity from layer-selective interactions in rhombohedral graphene

Hung Dinh Nguyen; Yafis Barlas

paper

Engineering kekule superconductivity from layer-selective interactions in rhombohedral graphene

arXiv:2608.18337

Abstract

At weak coupling, finite-momentum superconductivity is typically associated with broken time-reversal or inversion symmetry of the Fermi surface. Here, we show that lattice-scale pair-density-wave order in rhombohedral multilayer graphene can arise from layer/orbital-dependent pairing interactions, band chirality, and Dirac-point-centered Fermi surface topology while preserving both symmetries. Using mean-field theory and comparing finite momentum sectors $Q = \pm 2 K_{D}$ with the $Q = 0$ superconducting state, we find that layer-dependent interactions of opposite signs ( $V_{1 A} = - V_{J B} = - ∣ V ∣$ ) favor an intra-valley Kekulè state with center-of-mass momentum ( $Q = \pm 2 K_{D}$ ). In the presence of a time-reversal and inversion symmetry-preserving Kane-Mele mass ( $λ$ ), this state appears only above a critical carrier density ( $n_{K}^{cr i t} (λ, J)$ ). The two superconducting condensates exhibit opposite chirality, $J (- J)$ for $K_{D} (- K_{D})$ valleys, thereby preserving time-reversal and inversion symmetry. We map the phase diagram and analyze the dependence of $T_{c}$ on the chirality index $J$ and $λ$ . We also evaluate the superfluid stiffness in the Kekulè superconducting state, thereby determining the Berezinskii-Kosterlitz-Thouless (BKT) transition temperature. Our results show that orbital-dependent interactions in the presence of band chirality favor finite-momentum pairing in time-reversal and inversion symmetric Dirac materials.

10 pages