Inter-valley coherent order and isospin fluctuation mediated superconductivity in rhombohedral trilayer graphene

Shubhayu Chatterjee (), Taige Wang, Erez Berg and Michael P. Zaletel
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Shubhayu Chatterjee: University of California
Taige Wang: University of California
Erez Berg: Weizmann Institute of Science
Michael P. Zaletel: University of California

Nature Communications, 2022, vol. 13, issue 1, 1-10

Abstract: Abstract Superconductivity was recently discovered in rhombohedral trilayer graphene (RTG) in the absence of a moiré potential. Superconductivity is observed proximate to a metallic state with reduced isospin symmetry, but it remains unknown whether this is a coincidence or a key ingredient for superconductivity. Using a Hartree-Fock analysis and constraints from experiments, we argue that the symmetry breaking is inter-valley coherent (IVC) in nature. We evaluate IVC fluctuations as a possible pairing glue, and find that they lead to chiral unconventional superconductivity when the fluctuations are strong. We further elucidate how the inter-valley Hund’s coupling determines the spin-structure of the IVC ground state and breaks the degeneracy between spin-singlet and triplet superconductivity. Remarkably, if the normal state is spin-unpolarized, we find that a ferromagnetic Hund’s coupling favors spin-singlet superconductivity, in agreement with experiments. Instead, if the normal state is spin-polarized, then IVC fluctuations lead to spin-triplet pairing.

Date: 2022
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DOI: 10.1038/s41467-022-33561-w

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