28 research outputs found
Huge negative differential conductance in Au-H2 molecular nanojunctions
Experimental results showing huge negative differential conductance in
gold-hydrogen molecular nanojunctions are presented. The results are analyzed
in terms of two-level system (TLS) models: it is shown that a simple TLS model
cannot produce peaklike structures in the differential conductance curves,
whereas an asymmetrically coupled TLS model gives perfect fit to the data. Our
analysis implies that the excitation of a bound molecule to a large number of
energetically similar loosely bound states is responsible for the peaklike
structures. Recent experimental studies showing related features are discussed
within the framework of our model.Comment: 9 pages, 8 figure
Emergence of bound states in ballistic magnetotransport of graphene antidots
An experimental method for detection of bound states around an antidot formed
from a hole in a graphene sheet is proposed by measuring the ballistic two
terminal conductances. In particularly, we consider the effect of bound states
formed by magnetic field on the two terminal conductance and show that one can
observe Breit-Wigner like resonances in the conductance as a function of the
Fermi level close to the energies of the bound states. In addition, we develop
a new numerical method in which the computational effort is proportional to the
linear dimensions, instead of the area of the scattering region beeing typical
for the existing numerical recursive Green's function method.Comment: 7 pages, 6 figure
Conductance of Pd-H nanojunctions
Results of an experimental study of palladium nanojunctions in hydrogen
environment are presented. Two new hydrogen-related atomic configurations are
found, which have a conductances of ~0.5 and ~1 quantum unit (2e^2/h). Phonon
spectrum measurements demonstrate that these configurations are situated
between electrodes containing dissolved hydrogen. The crucial differences
compared to the previously studied Pt-H_2 junctions, and the possible
microscopic realizations of the new configurations in palladium-hydrogen
atomic-sized contacts are discussed.Comment: 4 pages, 4 figure
Atomic size oscillations in conductance histograms for gold nanowires and the influence of work hardening
Nanowires of different nature have been shown to self-assemble as a function
of stress at the contact between two macroscopic metallic leads. Here we
demonstrate for gold wires that the balance between various metastable nanowire
configurations is influenced by the microstructure of the starting materials
and we discover a new set of periodic structures, which we interpret as due to
the atomic discreteness of the contact size for the three principal crystal
orientations.Comment: This version corrects an error in attributing the three observed
periods, and includes a comparison with recent model calculation
Nanoscale spin-polarization in dilute magnetic semiconductor (In,Mn)Sb
Results of point contact Andreev reflection (PCAR) experiments on (In,Mn)Sb
are presented and analyzed in terms of current models of charge conversion at a
superconductor-ferromagnet interface. We investigate the influence of surface
transparency, and study the crossover from ballistic to diffusive transport
regime as contact size is varied. Application of a Nb tip to a (In,Mn)Sb sample
with Curie temperature Tc of 5.4 K allowed the determination of
spin-polarization when the ferromagnetic phase transition temperature is
crossed. We find a striking difference between the temperature dependence of
the local spin polarization and of the macroscopic magnetization, and
demonstrate that nanoscale clusters with magnetization close to the saturated
value are present even well above the magnetic phase transition temperature.Comment: 4 page
Quantum interference structures in the conductance plateaus of gold nanojunctions
The conductance of breaking metallic nanojunctions shows plateaus alternated
with sudden jumps, corresponding to the stretching of stable atomic
configurations and atomic rearrangements, respectively. We investigate the
structure of the conductance plateaus both by measuring the voltage dependence
of the plateaus' slope on individual junctions and by a detailed statistical
analysis on a large amount of contacts. Though the atomic discreteness of the
junction plays a fundamental role in the evolution of the conductance, we find
that the fine structure of the conductance plateaus is determined by quantum
interference phenomenon to a great extent.Comment: 4 pages, 4 figure