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arXiv · 2601.11055

Surface Functional Renormalization Group for Layered Quantum Materials

Lennart Klebl·Dante M. Kennes
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Abstract

We present an extension to the two-dimensional functional renormalization group to efficiently treat interactions on the surface or at interfaces of three-dimensional systems. As an application, we consider a semi-infinite stack of two-dimensional square lattices, including a Hubbard interaction on the surface layer and an alternating interlayer coupling. We investigate how strongly correlated states of the decoupled two-dimensional Hubbard model on the surface evolve under inclusion of such an SSH-like interlayer coupling. For large parts of the phase diagram as a function of the interlayer hopping parameters, the physics of the two-dimensional system prevails, with antiferromagnetic, superconducting $d$-wave, and ferromagnetic correlations taking center stage. However, for intermediate interlayer couplings the superconducting state at intermediate interaction strengths separates into two regimes by a small region of incommensurate spin-density-wave and spin-bond order, enabling the potential realization of chiral spin-bond order.

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Lennart Klebl, Dante M. Kennes. 2026-01-16. Surface Functional Renormalization Group for Layered Quantum Materials. https://doi.org/10.1002/andp.202600007

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