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In this work, an atomic force microscope (AFM) is combined with a confocal Raman spectroscopy setup to follow in situ the evolution of the G-band feature of isolated single-wall carbon nanotubes (SWNTs) under transverse deformation. The SWNTs are pressed by a gold AFM tip against the substrate where they are sitting. From eight deformed SWNTs, five exhibit an overall decrease in the Raman signal intensity, while three exhibit vibrational changes related to the circumferential symmetry breaking. Our results reveal chirality dependent effects, which are averaged out in SWNT bundle measurements, including a previously elusive mode symmetry breaking that is here explored using molecular dynamics calculations.

The electromechanical behavior of single-walled carbon nanotubes (SWNTs) in contact with different materials is investigated by scanning probe microscopy. An anomalous diamond/semiconducting nanotube behavior is observed, which is consistent with ab initio calculations: the formation of a broken-gap heterojunction between semiconducting SWNTs and a hydrogenated diamond surface results in a metallic response for such SWNTs.

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Using the generalized gradient approximation plus dynamical mean-field theory (GGA+DMFT) we confirm the importance of multi-orbital dynamical correlations in determining the paramagnetic insulating state of CrI 3 . While the ferromagnetic phase reveals weak electronic correlation effects due to strong spin-orbital polarization, the Mott insulating state of paramagnetic CrI 3 crystal is shown to be driven by the interplay between orbital-dependent one-electron lineshape and multi-orbital electronic interactions. To probe the paramagnetic Mott insulating state we performed x-ray absorption spectroscopy (XAS) measurements for the two structural phases of CrI 3 . Our study is relevant to understanding the orbital-selective electronic structure reconstruction of Mott insulators and should be applicable to other van der Waals bonded materials from bulk to the ultrathin limit.

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We perform first-principles investigations of two-dimensional, triangular lattices of Au 38 nanoparticles deposited on a graphene layer. We find that lattices of thiolate-covered nanoparticles cause electronic structure modifications in graphene such as minigaps, charge transfer, and new Dirac points, but graphene remains metallic. In contrast, for a moderate coverage of nanoparticles ͑Ϸ0.2 nm −2 ͒, a lattice of bare ͑noncovered͒ Au nanoparticles may induce periodic deformations on the graphene layer leading to the opening of a band gap of a few tens of meV at the Dirac point, in such a way that a properly charged system might become a semiconductor.

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