Electron-phonon interaction and the metal-insulator transition of the Si(111) surface |
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| Affiliation: | 1. Waste Management Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085, India;2. Theoretical Chemistry Section, Bhabha Atomic Research Centre, Trombay, Mumbai 400085, India;3. Fuel Chemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085, India;4. Radiation Biology & Health Sciences Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085, India;5. Radiochemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085, India;6. Nuclear Recycle Group, Bhabha Atomic Research Centre, Trombay, Mumbai 400085, India;7. Homi Bhabha National Institute, Anushaktinagar, Mumbai 400094, India;1. Radiochemistry Division, Bhabha Atomic Research Centre, Mumbai 400085, India;2. Homi Bhabha National Institute, Anushaktinagar, Mumbai 400094, India;3. Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400085, India;4. Radiological Safety Division, Atomic Energy Regulatory Board, Anushaktinagar, Mumbai 400094, India;5. Department of Chemistry, Illinois Institute of Technology, 3105 South Dearborn Street, Chicago, IL 60616, USA;1. Science and Technology on Plasma Physics Laboratory, Laser Fusion Research Center, China Academy of Engineering Physics, Mianyang, 621900, China;2. School of Physics and Electronics, Hunan University, Changsha, 410082, China;3. State Key Laboratory of Nuclear Physics and Technology, and Key Laboratory of HEDP of the Ministry of Education, CAPT, Peking University, Beijing, 100871, China |
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| Abstract: | On the basis of a microscopic theory of surface density response including local-field and excitonic effects we calculate the phonon spectrum of an ideal Si(111) slab. When these many-body effects are included, a drastic enhancement of the non-local response is obtained for a wavevector close to these corresponding to 7 × 7 superstructure. A saddle-point is created at the 2 × 1 wavevector. This result signals an excitonic insulator instability of the metallic dangling bond surface state. The coupling of the resulting charge-density wave to the lattice produces a soft surface mode with atomic displacements supporting the ionic buckling model. |
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