In nanowires made from gold atoms, electrons can only move in very narrow lanes, resulting in congestion. This is illustrated here by the red-stained wire. Depicted at the top right is the tip of a scanning tunneling microscope used by physicists to measure the electronic properties of nanowires. Image: Christian Blumenstein
electrons, the carriers of an electrical charge, crisscross through
metals or other electrically conductive materials. But this situation
changes as the conductors are made smaller and smaller.
physicists under Professor Ralph Claessen have taken miniaturization to
the extreme: their nanowires consist of single gold atoms arranged in
chains?it is not possible to go any smaller than that. In collaboration
with Professor René Matzdorf from the University of Kassel and Luc
Patthey from the Paul Scherrer Institute near Zurich, they have now
examined the electrical properties of these nanowires.
the nanowires, the electrons are so congested that they can only move
in one direction, namely along the wires. And even this bit of freedom
cannot be exploited to the full. They only move along in a stop-and-go
manner, just like cars in a jam on the freeway with just one lane at
their disposal: only when one car in the line of traffic moves forward a
bit can the others do likewise.
movements of the electrons in a nanowire are correlated just like
this,” says Matzdorf. “This means they can only absorb selected
energies, which is reflected in electrical conductivity and which we
have measured precisely in an experiment.”
electron jam has now been proven experimentally by Claessen’s team in
collaboration with their colleagues from Kassel and the Paul Scherrer
Institute. The scientists achieved this using highly sensitive measuring
techniques, scanning tunneling microscopy, and photoemission. This
enabled them to verify the unusual states of the electrons directly.
Their findings have been published in Nature Physics.
Why is a leading journal reporting the results of this research?
in atom chains we now have previously unknown capabilities for
measuring the properties of a one-dimensional quantum liquid,” says
Claessen. Physicists speak of a quantum liquid when the electrons are
confined in such narrow lanes. Theoreticians predicted the properties of
this “liquid” back in the 1960s. But very few of them have actually
been observed in experiments as well, until now.
Nanowires as the basis for success
Atomic building block: single gold atoms automatically form nanowires (left), which can then be connected deliberately using bridges or intentionally disrupted – by integrating other types of atom, for example, or by removing single gold atoms from the chains. Image: Christian Blumenstein
has taken decades to generate these special electron states
experimentally in atomic nanostructures. “This is mainly due to the fact
that the nanowires produced previously were too close together and
influenced each other, preventing the creation of a quantum liquid,”
explains Claessen’s colleague, Jörg Schäfer.
Würzburg physicists resolved this problem a good two years ago: using a
sophisticated procedure, they vapor deposit gold atoms onto germanium
plates such that they automatically arrange themselves into parallel
linear chains far enough apart from one another.
Next steps in the research
physicists now want to use the nanowires as an atomic building block.
They are thinking, for example, of inserting contacts between the wires
consisting of single atoms or molecules, which would equate to tiny
atomic switching elements. The intention behind this is to explore other
electronic phenomena at this smallest possible scale. Their findings
may well prove very valuable to the rapid miniaturization of electronic
components for computers, for example.