2021/02/28 by Gurjyot Sethi, Yinong Zhou, Linghan Zhu +2 · 103 citations
Materials Science · Physics and Astronomy · #2D Materials and Applications #Advanced Condensed Matter Physics #Atomic physics #Binding energy #Condensed matter physics #Diatomic molecule #Electron #Electronic and Structural Properties of Oxides #Exchange interaction #Exciton #Ground state #Lattice (music) #Molecule #Physics #Quantum mechanics #cond-mat.mtrl-sci #cond-mat.str-el
paper · pdf · doi:10.1103/physrevlett.126.196403
published in Physical Review Letters 126(19), 196403 (American Physical Society)
arxiv created 2021/04/15 · openalex publication_date 2021/05/12 · arxiv updated 2021/05/19 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/06
The excitonic insulator (EI) state is a strongly correlated many-body ground state, arising from an instability in the band structure toward exciton formation. We show that the flat valence and conduction bands of a semiconducting diatomic Kagome lattice, as exemplified in a superatomic graphene lattice, can possibly conspire to enable an interesting triplet EI state, based on density-functional theory calculations combined with many-body GW and Bethe-Salpeter equation. Our results indicate that massive carriers in flat bands with highly localized electron and hole wave functions significantly reduce the screening and enhance the exchange interaction, leading to an unusually large triplet exciton binding energy (∼1.1 eV) exceeding the GW band gap by ∼0.2 eV and a large singlet-triplet splitting of ∼0.4 eV. Our findings enrich once again the intriguing physics of flat bands and extend the scope of EI materials.