242 research outputs found
Conductance quantization and transport gap in disordered graphene nanoribbons
We study numerically the effects of edge and bulk disorder on the conductance
of graphene nanoribbons. We compute the conductance suppression due to
localization induced by edge scattering. We find that even for weak edge
roughness, conductance steps are suppressed and transport gaps appear. These
gaps are approximately inversely proportional to the nanoribbon width. On/off
conductance ratios grow exponentially with the nanoribbon length. Our results
impose severe limitations to the use of graphene in ballistic nanowires.Comment: 5 pages, 7 figures; references added, typos fixed, to appear in Phys.
Rev
The mesoscopic magnetron as an open quantum system
Motivated by the emergence of materials with mean free paths on the order of
microns, we propose a novel class of solid state radiation sources based on
reimplementing classical vacuum tube designs in semiconductors. Using materials
with small effective masses, these devices should be able to access the
terahertz range. We analyze the DC and AC operation of the simplest such
device, the cylindrical diode magnetron, using effective quantum models. By
treating the magnetron as an open quantum system, we show that it continues to
operate as a radiation source even if its diameter is only a few tens of
magnetic lengths.Comment: 11 pages, 7 figures; submitted to Physical Review Applie
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