Laser-induced effects on the electronic features of graphene nanoribbons

We study the interplay between lateral confinement and photon-induced processes on the electronic properties of illuminated graphene nanoribbons. We find that by tuning the device setup (edges geometries, ribbon width and polarization direction), a laser with frequency {Omega} may either not affect the electronic structure, or induce bandgaps or depletions at hbar {Omega}/2, and/or at other energies not commensurate with half the photon energy. Similar features are also observed in the dc conductance, suggesting the use of the polarization direction to switch on and off the graphene device. Our results could guide the design of novel types of optoelectronic nano-devices.

Efficient linear scaling method for computing the thermal conductivity of disordered materials

An efficient order$-N$ real-space Kubo approach is developed for the calculation of the thermal conductivity of complex disordered materials. The method, which is based on the Chebyshev polynomial expansion of the time evolution operator and the Lanczos tridiagonalization scheme, efficiently treats the propagation of phonon wave-packets in real-space and the phonon diffusion coefficients. The mean free paths and the thermal conductance can be determined from the diffusion coefficients. These quantities can be extracted simultaneously for all frequencies, which is another advantage in comparison with the Greens function based approaches. Additionally, multiple scattering phenomena can be followed through the time dependence of the diffusion coefficient deep into the diffusive regime, and the onset of weak or strong phonon localization could possibly be revealed at low temperatures for thermal insulators. The accuracy of our computational scheme is demonstrated by comparing the calculated phonon mean free paths in isotope-disordered carbon nanotubes with Landauer simulations and analytical results. Then, the upscalibility of the method is illustrated by exploring the phonon mean free paths and the thermal conductance features of edge disordered graphene nanoribbons having widths of $sim$20 nanometers and lengths as long as a micrometer, which are beyond the reach of other numerical techniques. It is shown that, the phonon mean free paths of armchair nanoribbons are smaller than those of zigzag nanoribbons for the frequency range which dominate the thermal conductance at low temperatures. This computational strategy is applicable to higher dimensional systems, as well as to a wide range of materials.

Point Mutations Effects on Charge Transport Properties of the Tumor-Suppressor Gene p53

We report on a theoretical study of point mutations effects on charge transfer properties in the DNA sequence of the tumor-suppressor p53 gene. On the basis of effective single-strand or double-strand tight-binding models which simulate hole propagation along the DNA, a statistical analysis of charge transmission modulations associated with all possible point mutations is performed. We find that in contrast to non-cancerous mutations, mutation hotspots tend to result in significantly weaker {em changes of transmission properties}. This suggests that charge transport could play a significant role for DNA-repairing deficiency yielding carcinogenesis.