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April 24th 2019

A wire that consists of a carbon nanotube can be used for electronic transport. However, electrons in the tube only have a limited freedom of movement. The researchers from this programme are studying the influence of light and temperature on the behaviour of these electrons.

In wires made from carbon nanotubes, electrons can only move along the length of the tubes. Such a one-dimensional electron system is called a Tomonaga-Luttinger liquid. Due to the one-dimensional character, all of the electrons in the wire will 'feel' each other. This leads to a fundamentally new collective behaviour of the electrons. An important measurable effect of the interaction between electrons is a reduced electrical conduction at low voltage and temperature.

Isolated tubes
In this programme, the researchers will study the behaviour of freely hanging carbon nanotubes. By minimising the contact between the nanotubes and their surroundings, the heat loss from the nanotubes will be extremely small. And, as the nanotubes have a very small volume, adding just a limited quantity of energy can cause the tubes to heat up considerably .

If far-infrared light falls on a nanotube, the temperature of the electrons in the tube will increase. This increase in temperature affects the electrical transport in two different ways. First of all it partially cancels the suppression of the conduction by the one-dimensional state. By observing the freely hanging tubes the researchers can for the first time study the influence of temperature in the nanotubes without heating up their surroundings as well. The second effect arises due to the temperature difference at the contacts between the carbon nanotube and the metal electrodes. As a result of the temperature increase, a difference occurs in the number of electrons and holes transported at the contacts. This gives rise to a potential difference across the contacts.

These two effects offer insights into the behaviour of electrons in an environment with limited freedom of movement. Furthermore the experiment could provide a way of measuring infrared light, by describing the changes in the transport due to incident light.