3 research outputs found
Enhanced Magnetoresistance in Molecular Junctions by Geometrical Optimization of Spin-Selective Orbital Hybridization
Molecular junctions based on ferromagnetic
electrodes allow the study of electronic spin transport near the limit
of spintronics miniaturization. However, these junctions reveal moderate
magnetoresistance that is sensitive to the orbital structure at their
ferromagnet–molecule interfaces. The key structural parameters
that should be controlled in order to gain high magnetoresistance
have not been established, despite their importance for efficient
manipulation of spin transport at the nanoscale. Here, we show that
single-molecule junctions based on nickel electrodes and benzene molecules
can yield a significant anisotropic magnetoresistance of up to ∼200%
near the conductance quantum <i>G</i><sub>0</sub>. The measured
magnetoresistance is mechanically tuned by changing the distance between
the electrodes, revealing a nonmonotonic response to junction elongation.
These findings are ascribed with the aid of first-principles calculations
to variations in the metal–molecule orientation that can be
adjusted to obtain highly spin-selective orbital hybridization. Our
results demonstrate the important role of geometrical considerations
in determining the spin transport properties of metal–molecule
interfaces
Molecule-Adsorbed Topological Insulator and Metal Surfaces: A Comparative First-Principles Study
We
compare electronic structure characteristics of three different
kinds of benzene-adsorbed (111) surfaces: that of Bi<sub>2</sub>Te<sub>3</sub>, a prototypical topological insulator, that of Au, a prototypical
inert metal, and that of Pt, a prototypical catalytic metal. Using
first-principles calculations based on dispersion-corrected density
functional theory, we show that benzene is chemisorbed on Pt, but
physisorbed on Au and Bi<sub>2</sub>Te<sub>3</sub>. The adsorption
on Bi<sub>2</sub>Te<sub>3</sub> is particularly weak, consistent with
a minimal perturbation of the electronic structure at the surface
of the topological insulator, revealed by a detailed analysis of the
interaction of the molecular orbitals with the topological surface
states
Probing the Orbital Origin of Conductance Oscillations in Atomic Chains
We investigate periodical oscillations
in the conductance of suspended
Au and Pt atomic chains during elongation under mechanical stress.
Analysis of conductance and shot noise measurements reveals that the
oscillations are mainly related to variations in a specific conduction
channel as the chain undergoes transitions between zigzag and linear
atomic configurations. The calculated local electronic structure shows
that the oscillations originate from varying degrees of hybridization
between the atomic orbitals along the chain as a function of the zigzag
angle. These variations are highly dependent on the directionally
and symmetry of the relevant orbitals, in agreement with the order-of-magnitude
difference between the Pt and Au oscillation amplitudes observed in
experiment. Our results demonstrate that the sensitivity of conductance
to structural variations can be controlled by designing atomic-scale
conductors in view of the directional interactions between atomic
orbitals