Frenkel–Kontorova Domains of Single-layer Pb Intercalated between SiC and Graphene

Confinement heteroepitaxy (CHet) [1] can intercalate Pb atoms between a SiC substrate and graphene to form a single layer which is a potential platform for investigating spin phenomena like momentum-space spin antivortices [2]. ARPES results align well with the calculated band structure of a model where Pb atoms register 1⨉1 above the uppermost Si atoms in SiC [3, 4]. However, due to the large size of Pb atoms, this 1⨉1 registry suffers compressive stress and the exact atomic structure of the intercalated Pb layer remains unclear [3-6]. By performing first-principles structural relaxation of systems containing vacancy lines that release the compressive stress, we find that Frenkel–Kontorova domains are formed whose energetically favored size agrees well with that observed in STM measurements [4, 6, 7]. This Frenkel–Kontorova domain model does not conflict with the ARPES results because Pb atoms inside the majority of the domain maintain a near 1⨉1 registry while Pb atoms at the domain boundary more rapidly shift registry while losing real-space periodicity, thus ARPES only picks up discernible signals from the structure inside the domain.

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[3] B. Matta et al., Phys. Rev. Research 4, 023250 (2022).

[4] P. Schädlich et al., Advanced Materials Interfaces 2300471 (2023).

[5] J. Wang et al., Phys. Rev. B 103, 085403 (2021).

[6] T. Hu et al., Carbon 179, 151 (2021).

[7] A. Yurtsever et al., Small 12, 3956 (2016).