Abstracts Book - IMRC 2018

• SC6-P005
HEAT TRANSPORT THROUGH ATOMIC AND MOLECULAR
JUNCTIONS
Kloeckner Jan 1,2
1 Okinawa Institute of Science and Technology Graduate University, , Japan. 2 Universität
Konstanz, Department of Physics, Germany.
Understanding heat transport at the nanoscale is of fundamental importance
for the development of novel nanoelectronic and nanophononic devices [1]. By
using non-equilibrium Green’s function techniques combined with density
functional theory (DFT) for modeling the electronic structure, we investigate
heat transport in atomic and molecular junctions.
We show our recent results, aiming at understanding fundamental issues
related to heat transport at the nanoscale: (a) the length dependence of heat
transport [2], (b) the thermal conductance of single-atom junctions [3] and (c)
interference effects in benzene derivatives with side groups [4]. Furthermore,
we present how to analyze phonon transmission in terms of transmission
eigenchannels, which provides a direct link between transmission and the
vibrational modes the molecular system [5].
For the study of the length dependence we investigate alkane chains, attached
to gold electrodes with different anchors. Their form is Au-X-(CY 2 ) n -X-Au with
X=NH 2 ,S, Y=H,F and n=2,4,...,30. We find the thermal conductance to be largely
length-independent, indicating ballistic transport. Furthermore our study of
different anchors shows the possibillity to tune the thermal conductance.
Especially for fluorinated alkane molecules this effect is very pronounced. To
clarify the role of the electrons in such junctions, we also calculate the thermal
conductance of these heat carriers.
In the study of the thermal conductance of a single-atom junction we could
demonstrate, together with the experimental group of E. Meyhofer and P. Reddy
at the University of Michigan, that the contribution the electrons to the thermal
conductance is quantized in gold junctions and that the Wiedemann-Franz law
holds down to the nanoscale. For this we combined firstly a statistical approach
based on molecular dynamics simulations with a tight-binding parametrization
for the electronic transport and secondly our DFT-based calculations. By
sampling the phase space of the geometric configurations, we could