Kinetic Blockade and Filamentary Pair Density Waves in Strain-Engineered Graphene

Abstract

We investigate superconductivity in strain-engineered graphene using a self-consistent Bogoliubov-de Gennes approach. Challenging the paradigm that the high density of states in flat bands universally enhances pairing, we identify a "kinetic blockade" mechanism: strain-induced sublattice polarization segregates electronic states, rendering these singularities inert. Instead, superconductivity emerges as robust filaments at geometric nodes, forming a pair density wave. This state features a sign-reversing order parameter, detectable via impurity-induced zero-energy modes. Our findings reveal a unique geometric origin for filamentary superconductivity, offering new perspectives on strain-tuned quantum phases in Dirac materials.

Figures (4)

• Figure 1: Electronic structure of the corrugated graphene in the normal state. (a) Schematic illustration of the sinusoidally strain-engineered graphene lattice. (b) The calculated energy band structure along $k_y$​, exhibiting flat bands at zero energy induced by the PMF. (c) Spatial profile of the zero-energy LDOS along the corrugated direction $x$. The solid (dashed) lines represent the A (B) sublattice, revealing a distinct spatial separation of the zeroth pseudo-Landau levels. (d) Energy-dependent LDOS at $x=0.33L$, showing a sharp peak at the Fermi level for the A-sublattice (solid line) and a gap for the B-sublattice (dashed line).
• Figure 2: Spatial dissociation of superconductivity and the emergence of a PDW. (a) Self-consistent profile of the superconducting order parameter amplitude $|\Delta(x)|$ along the corrugation. The maximum pairing amplitude emerges at the geometric nodes, whereas the flat-band regions (marked by arrows) exhibit suppressed pairing despite the high DOS. (b) Schematic representation of the superconducting phase on the graphene lattice in the high-$\Delta$ region. The solid (blue) and hollow (red) circles represent sites with opposite signs of the order parameter ($\pm$), illustrating the formation of a sign-reversing PDW state.
• Figure 3: LDOS in the superconducting state. (a) LDOS in the flat-band region ($x=0.33L$). The strong sublattice polarization persists (dashed vs. solid lines), but the original normal-state zero-energy peak is split, indicating the opening of a partial superconducting gap. (b) LDOS at the node of corrugation ($x=0.5L$), where the sublattice symmetry is restored.
• Figure 4: Detection of the PDW state via non-magnetic impurity scattering. The LDOS at a nearest-neighbor site of a non-magnetic impurity located in the superconducting region is plotted for various impurity strengths $V_i$.