Surface state bi-polarons formation on a triangular lattice in the sp-type alkali/Si(111) Mott insulator

2009/07/09 by Luis Cardenas, L. A. Cardenas, Y. Fagot‐Révurat +10
Physics and Astronomy · #Advanced Chemical Physics Studies #FOS: Physical sciences #Quantum and electron transport phenomena #Strongly Correlated Electrons (cond-mat.str-el) #Superconductivity (cond-mat.supr-con) #Surface and Thin Film Phenomena #cond-mat.str-el #cond-mat.supr-con

paper · pdf · doi:10.48550/arxiv.0907.1573

4 pages, 3 figures. accepted in Physical Review Letters (2009)

arxiv created 2009/07/09 · openalex publication_date 2009/07/09 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28

Abstract

We report on new LEED, STM and ARPES studies of alkali/Si(111) previously established as having a Mott insulating ground state at surface. The observation of a strong temperature dependent Franck-Condon broadening of the surface band together with the novel √(3)×√(3)→2(√(3)×√(3)) charge and lattice ordering below 270 K evidence a surface charge density wave (SCDW) in the strong e-ph coupling limit (g≈8). Both the adiabatic ratio ℏω₀/t≈0.8 and the effective pairing energy V_eff=U-2gℏω₀≈-800 meV are consistent with the possible formation of a bi-polaronic insulating phase consisting of alternating doubly-occupied/unoccupied dangling bonds as expected in the Holstein-Hubbard model.

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