Superconductivity from Repulsive Interactions in Rhombohedral Trilayer Graphene: a Kohn-Luttinger-Like Mechanism

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What is a Kohn-Luttinger-Like Mechanism in simple words?

AI: A Kohn-Luttinger-Like Mechanism, in simple words, refers to the process by which superconductivity emerges in a material due to repulsive interactions between electrons. Specifically, in rhombohedral trilayer graphene, the long-range Coulomb repulsion between electrons plays a key role in driving the superconducting phase. Unlike other systems where attractive interactions are responsible for superconductivity, in rhombohedral trilayer graphene, the superconducting order parameter is spin-triplet and exhibits modulation within each valley pocket of the Fermi surface. The critical temperature of the superconducting phase depends on the electron filling and reaches its highest point when the density of states diverges. Essentially, the Kohn-Luttinger-Like Mechanism describes how superconductivity can be achieved through these repulsive interactions between electrons.


Tommaso Cea, Pierre A. Pantaleón, Vo Tien Phong, Francisco Guinea


We study the emergence of superconductivity in rhombohedral trilayer graphene due purely to the long-range Coulomb repulsion. This repulsive-interaction-driven phase in rhombohedral trilayer graphene is significantly different from those found in twisted bilayer and trilayer graphenes. In the latter case, the nontrivial momentum-space geometry of the Bloch wavefunctions leads to an effective attractive electron-electron interaction; this allows for less modulated order parameters and for spin-singlet pairing. In rhombohedral trilayer graphene, we instead find spin-triplet superconductivity with critical temperatures up to 0.15 K. The critical temperatures strongly depend on electron filling and peak where the density of states diverge. The order parameter shows a significant modulation within each valley pocket of the Fermi surface.

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