Anomalous Quantum Oscillations in a Heterostructure of Graphene on a Proximate Quantum Spin Liquid

The quasi-two-dimensional Mott insulator alpha-RuCl3 is proximate to the sought-after Kitaev quantum spin liquid (QSL). In a layer of alpha-RuCl3 on graphene, the dominant Kitaev exchange is further enhanced by strain. Recently, quantum oscillation (QO) measurements of such alpha-RuCl3 and graphene heterostructures showed an anomalous temperature dependence beyond the standard Lifshitz-Kosevich (LK) description. Here, we develop a theory of anomalous QO in an effective Kitaev-Kondo lattice model in which the itinerant electrons of the graphene layer interact with the correlated magnetic layer via spin interactions. At low temperatures, a heavy Fermi liquid emerges such that the neutral Majorana fermion excitations of the Kitaev QSL acquire charge by hybridizing with the graphene Dirac band. Using ab initio calculations to determine the parameters of our low-energy model, we provide a microscopic theory of anomalous QOs with a non-LK temperature dependence consistent with our measurements. We show how remnants of fractionalized spin excitations can give rise to characteristic signatures in QO experiments.

Automated summary

In this study, a theory of anomalous quantum oscillations (QOs) in an effective Kitaev-Kondo lattice model is developed, revealing the interaction mechanism between itinerant electrons of the graphene layer and the correlated magnetic layer through spin interactions. At low temperatures, a heavy Fermi liquid emerges, where neutral Majorana fermion excitations of the Kitaev QSL acquire charge by hybridizing with the graphene Dirac band.