1. Sep 13, 2006 2nd NIRT Meeting, DuPontSlava V Rotkin Band structure of single-wall carbon nanotube modulated by DNA wrap Physics Department & Center for Advanced Materials and Nanotechnology Lehigh University Stacy E. Snyder, Vadim I. Puller Slava V. Rotkin

2. Sep 13, 2006 2nd NIRT Meeting, DuPontSlava V Rotkin DNA-NT complexes

3. Sep 13, 2006 2nd NIRT Meeting, DuPontSlava V Rotkin Preliminary modeling DNA strands are known to form a helical hybrids with NTs. DNA backbone is charged (about one electron per 7 Å) Strong potential may cause band gap opening in a metallic NT How to model the system? - commensurate wrap - delta-wire approximation

4. Sep 13, 2006 2nd NIRT Meeting, DuPontSlava V Rotkin Preliminary modeling DNA strands are known to form a helical hybrids with NTs. Gap opening in [5,5] NT {R:1} wrap: - Mod3[R]=0 - Mod3[R]=1,-1 DNA backbone is charged (about one electron per 7 Å) Strong potential may cause band gap opening in a metallic NT How to model the system? - commensurate wrap - delta-wire approximation

5. Sep 13, 2006 2nd NIRT Meeting, DuPontSlava V Rotkin Toy Model Two-parameter toy model : compromise accuracy and relevancy

6. Sep 13, 2006 2nd NIRT Meeting, DuPontSlava V Rotkin Tight-binding results Self-consistent solution for the charge density of semiconductor [7,0] zigzag NT under DNA wrap perturbation

7. Sep 13, 2006 2nd NIRT Meeting, DuPontSlava V Rotkin Tight-binding results Self-consistent solution for the charge density of semiconductor [7,0] zigzag NT under DNA wrap perturbation Polarization interaction: for [7,0] NT and {6:1 | 4e} wrap the cohesion energy due to the NT pi-e- system polarization   ~ 0.47 eV/b.p. interaction with the image charge overestimates C.E. image charge for semiconductor

8. Sep 13, 2006 2nd NIRT Meeting, DuPontSlava V Rotkin Band renormalization The (6,5) nanotube is prominent in samples of DNA-nanotube hybrids. Its wrapping has pitch ~ 18 nm, corresponding to ~1 winding of DNA in 4 unit cells of the bare nanotube, and this ratio was used in modeling. Pristine [6,5] NT [6,5] NT-DNA hybrid

9. Sep 13, 2006 2nd NIRT Meeting, DuPontSlava V Rotkin Continuum Field Models

10. Sep 13, 2006 2nd NIRT Meeting, DuPontSlava V Rotkin Rudimentary Field Model U 0 – potential strength, λ 0 –potential width, φ–offset parameter States near Fermi level depend only on the model potential

11. Sep 13, 2006 2nd NIRT Meeting, DuPontSlava V Rotkin Rudimentary Field Model n E g /V 0 [5,5] [7,7][8,8] States near Fermi level Numerical modeling of delta-wire Fixed NT chirality (A) Fixed DNA helicity Variation of R(n)

12. Sep 13, 2006 2nd NIRT Meeting, DuPontSlava V Rotkin Symmetry breaking (Q) a)b)c) (a) Pristine NT; (b) NT with z-type perturbation; (c) NT with a-type perturbation One obtains a qualitative picture from heuristic arguments

13. Sep 13, 2006 2nd NIRT Meeting, DuPontSlava V Rotkin Field Model: Details

14. Sep 13, 2006 2nd NIRT Meeting, DuPontSlava V Rotkin Symmetry breaking (A) bare Hamiltonian of metallic NT perturbation of type AAAA perturbation of type ABAB

15. H A /3 A A A A A A B HZHZ a1a1 a2a2 b

16. Sep 13, 2006 2nd NIRT Meeting, DuPontSlava V Rotkin Symmetry analysis

17. Sep 13, 2006 2nd NIRT Meeting, DuPontSlava V Rotkin Symmetry breaking (N) Size of the linear gap due to a helical perturbation as a function of the indices M and n. Diameter of a circle is proportional to the gap value. Color assignment for the symmetry breaking mechanisms: green - (Ze), light green - (Zo), light blue - (A1e), blue - (A2e), orange - (A1o), red - (A2o). Armchair NT

18. Sep 13, 2006 2nd NIRT Meeting, DuPontSlava V Rotkin Symmetry breaking (N)

19. Sep 13, 2006 2nd NIRT Meeting, DuPontSlava V Rotkin Symmetry breaking (N)

20. Sep 13, 2006 2nd NIRT Meeting, DuPontSlava V Rotkin Symmetry breaking (N)

21. Sep 13, 2006 2nd NIRT Meeting, DuPontSlava V Rotkin