  In this work we present an ab-initio study of electronic properties of 1
dimensional (1D) core-shell nanostructures made of MS2 (MoS2, WS2) or BN
armchair nanotube encapsulated carbon nanotubes (CNT). With local density
approximation (LDA) in density functional theory (DFT) we calculate the
bandstructure, carrier effective masses, various fundamental electrostatic
features and optical absorption in such core-shell tubes. The carrier transport
in these structures are important for nanoelectronics applications and are
studied with the Greens function formalism. Simulations show a moderate
indirect band gap in the core-shell CNT@MS2 tubes while the CNT@BN shows
metallic nature. The varying chirality of CNT strongly affects the carrier
effective masses of the CNT@MS2 structure. Electron density is found to be much
more localized near the atom cores and stronger in magnitude for the CNT@BN
while the W atoms show a more prominent electron-gas presence around them than
Mo atoms as found in the electron localization functions. In the CNT@MS2
systems the electrostatic difference potential indicates a drive to transfer
charge from the metal to the S atoms in the shell. In terms of optical
absorption a strong and sharper peak is observed around 6 eV for the CNT@BN
compared to a more broad absorption spectra of the CNT@MS2. Metallic
transmission spectra is seen for CNT@BN while CNT@MS2 shows non-metallic
transport but with a larger number of transmission states near fermi level. The
electronic and optical properties and its possible tuning in the core-shell
structures can be useful in various applications such as shielded
interconnects, logic switches and optoelectronics.
