17,806 research outputs found
Quantum phonon transport of molecular junctions amide-linked with carbon nanotubes: a first-principle study
Quantum phonon transport through benzene and alkane chains amide-linked with
single wall carbon nanotubes (SWCNTs) is studied within the level of density
functional theory. The force constant matrices are obtained from standard
quantum chemistry software. The phonon transmission and thermal conductance are
from the nonequilibrium Green's function and the mode-matching method. We find
that the ballistic thermal conductance is not sensitive to the compression or
stretching of the molecular junction. The terminating groups of the SWCNTs at
the cutting edges only influence the thermal conductance quantitatively. The
conductance of the benzene and alkane chains shows large difference. Analysis
of the transmission spectrum shows that (i) the low temperature thermal
conductance is mainly contributed by the SWCNT transverse acoustic modes, (ii)
the degenerate phonon modes show different transmission probability due to the
presence of molecular junction, (iii) the SWCNT twisting mode can hardly be
transmitted by the alkane chain. As a result, the ballistic thermal conductance
of alkane chains is larger than that of benzene chains below 38 K, while it is
smaller at higher temperature.Comment: 5 pages, 5 figure
Low Frequency Quantum Transport in a Three-probe Mesoscopic Conductor
The low frequency quantum transport properties of a three-probe mesoscopic
conductor are studied using B\"uttiker's AC transport formalism. The static
transmission coefficients and emittance matrix of the system were computed by
explicitly evaluating the various partial density of states (PDOS). We have
investigated the finite size effect of the scattering volume on the global
PDOS. By increasing the scattering volume we observed a gradual improvement in
the agreement of the total DOS as computed externally or locally. Our numerical
data permits a particular fitting form of the finite size effect.Comment: 13 pages, LaTeX, submitted to Phys. Rev.
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