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arXiv 0907.1573cond-mat.str-elcond-mat.supr-con
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sp型碱金属/Si(111)莫特绝缘体三角晶格表面态双极化子的形成

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

L. A. Cardenas, Y. Fagot-Revurat, L. Moreau, B. Kierren, D. Malterre

摘要:

我们报道了新的LEED,STM和ARPES研究碱/Si(111)先前建立了一个莫特绝缘基态在表面。在270 K以下观察到的强温度依赖性的表面能带的Franck-Condon增宽以及新的$\sqrt{3}\times\sqrt{3}\to2(\sqrt{3}\times\sqrt{3})$电荷和晶格有序证明了在强e-ph耦合极限($g\approx8$)中的表面电荷密度波(SCDW)。绝热比$\hbarω_0/t\approx0.8$和有效配对能$V_{eff}=U-2g\hbarω_0\approx-800$ $meV$与Holstein-哈伯德模型中预期的由交替的双占据/未占据悬挂键组成的双极化绝缘相的可能形成一致。

英文摘要:

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 $\sqrt{3}\times\sqrt{3}\to2(\sqrt{3}\times\sqrt{3})$ charge and lattice ordering below 270 K evidence a surface charge density wave (SCDW) in the strong e-ph coupling limit ($g\approx8$). Both the adiabatic ratio $\hbarω_0/t\approx0.8$ and the effective pairing energy $V_{eff}=U-2g\hbarω_0\approx-800$ $meV$ 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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