1,154 research outputs found
Spin quantum tunneling in single molecular magnets: fingerprints in transport spectroscopy of current and noise
We demonstrate that transport spectroscopy of single molecular magnets shows
signatures of quantum tunneling at low temperatures. We find current and noise
oscillations as function of bias voltage due to a weak violation of spin
selection rules by quantum tunneling processes. The interplay with Boltzmann
suppression factors leads to fake resonances with temperature-dependent
position which do not correspond to any charge excitation energy. Furthermore,
we find that quantum tunneling can completely suppress transport if the
easy-plane anisotropy has a high symmetry.Comment: 4 pages, 3 figure
Quantum tunneling induced Kondo effect in single molecular magnets
We consider transport through a single-molecule magnet strongly coupled to
metallic electrodes. We demonstrate that for half-integer spin of the molecule
electron- and spin-tunneling \emph{cooperate} to produce both quantum tunneling
of the magnetic moment and a Kondo effect in the linear conductance. The Kondo
temperature depends sensitively on the ratio of the transverse and easy-axis
anisotropies in a non-monotonic way. The magnetic symmetry of the transverse
anisotropy imposes a selection rule on the total spin for the occurrence of the
Kondo effect which deviates from the usual even-odd alternation.Comment: 4 pages, 4 figure
Influence of nano-mechanical properties on single electron tunneling: A vibrating Single-Electron Transistor
We describe single electron tunneling through molecular structures under the
influence of nano-mechanical excitations. We develop a full quantum mechanical
model, which includes charging effects and dissipation, and apply it to the
vibrating C single electron transistor experiment by Park {\em et al.}
{[Nature {\bf 407}, 57 (2000)].} We find good agreement and argue vibrations to
be essential to molecular electronic systems. We propose a mechanism to realize
negative differential conductance using local bosonic excitations.Comment: 7 pages, 6 figure
Transport signature of pseudo-Jahn-Teller dynamics in a single-molecule transistor
We calculate the electronic transport through a molecular dimer, in which an
excess electron is delocalized over equivalent monomers, which can be locally
distorted. In this system the Born-Oppenheimer approximation breaks down
resulting in quantum entanglement of the mechanical and electronic motion. We
show that pseudo Jahn-Teller (pJT) dynamics of the molecule gives rise to
conductance peaks that indicate this violation. Their magnitude, sign and
position sharply depend on the electro-mechanical properties of the molecule,
which can be varied in recently developed three-terminal junctions with
mechanical control. The predicted effect depends crucially on the degree of
intramolecular delocalization of the excess electron, a parameter which is also
of fundamental importance in physical chemistry.Comment: 6 pages, 3 figure
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