Electron correlations in the clean and hydrogen-covered Si(111)-<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mo>(</mml:mo><mml:mn>7</mml:mn><mml:mn /><mml:mo>×</mml:mo><mml:mn>7</mml:mn><mml:mo>)</mml:mo></mml:math>surface at extremely low Li coverages

Fick, D.; Veith, Richard C.; Ebinger, H.D.; Jänsch, H.J.; Weindel, C.; Winnefeld, H.; Paggel, J. J.

doi:10.1103/physrevb.60.8783

Cited by 13 publications

(11 citation statements)

References 53 publications

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“…As compared to the previous experiments 12,38 it is now possible to extend the present ones to much higher magnetic fields and to much lower temperatures. Whereas high magnetic fields suppress considerably diffusive contributions to the T 1 -times, low temperatures proved to enhance spectroscopic details in the past.…”

Section: Introductionsupporting

confidence: 49%

“…There, within quite large error bars, a linear increase of the relaxation rates was observed. 12,38 As will be argued within the discussion of our model describing the new data at the end of Sec. III C, this change in temperature dependence is probably correlated with our new surface preparation technique.…”

Section: A Experimental Resultsmentioning

confidence: 91%

“…In contrast to our previous publications 12,18,38 DOS͑E͒ denotes now the electron density of states for one spin direction only. ͉⌽ F ͑0͉͒ 2 denotes the probability to find at E F an electron at the nucleus.…”

Section: A Schematic Modelmentioning

confidence: 83%

“…45,46 Heating was available by electron bombardment from the rear, cooling by contact to a liquid helium reservoir, instead of a LN 2 one as in previous experiments. 12,18,38 The lowest temperature reached at the Si crystal was 50 K.…”

Section: Experimental Technique and Setupmentioning

confidence: 99%

“…We therefore resumed our ␤-NMR experiments on extremely dilute 8 Li adsorbates on the Si͑111͒-͑7 ϫ 7͒ surface. 12,38 The total Li coverage amounted to 10 −3 monolayer ͑ML͒ at most. That is in the average one Li atom per 20 ͑7 ϫ 7͒ unit cells.…”

Section: Introductionmentioning

confidence: 99%

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MetallicSi(111)−(7×7)-reconstruction: A surface close to a Mott-Hubbard metal-insulator transition

et al. 2005

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Li adsorption at extremely low coverages ͑10 −3 ML and below͒ on the metallic Si͑111͒-͑7 ϫ 7͒ surface has been studied by ␤-NMR experiments ͑measurement of T 1 -times͒. Instead of increasing linearly with the sample temperature, as expected for a metallic system, the relaxation rate ␣ =1/T 1 is almost constant in between 50 K and 300 K sample temperature and rises considerably above. Comparison with T 1 -times around 900 K ͑ob-served with 6 Li-NMR͒ excludes adsorbate diffusion as the cause of the relaxation rate. Thus the almost temperature independent relaxation rate below 300 K points to an extremely localized and thus narrow band ͑width about 10 meV͒ which pins the Fermi energy. It is responsible for the metallicity of the ͑7 ϫ 7͒-reconstruction. Because of the steeply rising relaxation rate beyond 300 K this narrow band is located energetically within a gap ͑approximately 100-500 meV wide͒ in between a lower filled and an upper empty ͑Hubbard͒ band. Due to its extremely narrow width it can hardly be detected in photo electron experiments. In dynamical mean field theories based on Hubbard Hamiltonians this kind of density of states is typical for correlated electron systems close to a Mott-Hubbard metal-insulator transition.

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Section: Introductionsupporting

confidence: 49%

Section: A Experimental Resultsmentioning

confidence: 91%