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Á. Gali

Publications and source records attributed to Á. Gali.

2 recordsLinked to original sources

Super-resolution Airy disk microscopy of individual color centers in diamond

Super-resolution imaging techniques enable nanoscale microscopy in fields such as physics, biology, and chemistry. However, many super-resolution techniques require specialized optical components, such as a helical-phase mask. We present a novel technique, Super-resolution Airy disk Microscopy (SAM) that can be used in a standard confocal microscope without any specialized optics. We demonstrate this technique, in combination with ground state depletion, to image and control nitrogen-vacancy (NV) centers in bulk diamond below the diffraction limit. A greater than 14-fold improvement in resolution compared to the diffraction limit is achieved, corresponding to a spatial resolution of 16.9(8) nm for a 1.3 NA microscope with 589 nm light. We make use of our enhanced spatial resolution to control the spins states of individual NV centers separated from each other by less than the diffraction limit, including pairs sharing the same orientation that are indistinguishable with a conventional electron spin resonance measurement.

physics.optics

Inter-shell interaction in double walled carbon nanotubes: charge transfer and orbital mixing

Recent nuclear magnetic resonance measurements on isotope engineered double walled carbon nanotubes (DWCNTs) surprisingly suggest a uniformly metallic character of all nanotubes, which can only be explained by the interaction between the layers. Here we study the inter-shell interaction in DWCNTs by density functional theory and inter-molecular Hückel model. We find charge transfer between the layers using both methods. We show that not only does the charge transfer appear already at the fundamental level of the inter-molecular Hückel model, but also that the spatial distribution of the change in the electron density is well described already at this level of theory. We find that the charge transfer between the walls is on the order of 0.001 e/atom and that the inner tube is always negatively charged. We also observe orbital mixing between the states of the layers. We find that these two effects combined can in some cases lead to a semiconductor--to--metal transition of the double walled tube, but not necessarily in all cases.

cond-mat.mtrl-sci