Overview

Applications are invited for the above fixed-term postdoctoral fellowship to investigate the effects of vibronic coupling in fullerenes, which will be funded through an EPSRC project grant. The work will involve theoretical and computational modelling of Jahn-Teller effects in fullerene ions in solids and on surfaces with a view to understanding the results of experimental measurements, such as scanning tunneling microscopy (STM) imaging and spectroscopy, on these ions.

Further scientific details

Fullerenes are closed-cage structures of pure carbon with atoms at the vertices of pentagonal and hexagonal faces. The most abundant of the fullerenes is C₆₀, whose icosahedral symmetry is the highest possible in nature. This leads to many unique properties, which have been the subject of much research over the last two decades. C₆₀-based solids are particularly interesting because changes to the charge state or environment can drastically alter the electrical and magnetic properties. Some compounds of the form A₃C₆₀ (A = alkali metal) can be superconducting up to around 40K, whilst the A₄C₆₀ materials are insulators. Fullerene molecules are also interesting adsorbates on surfaces. Individual molecules can adopt different orientations when they bind to a surface, with interactions between molecules leading to further orientational arrangements and ordered phases. Low temperature scanning tunnelling microscopy (STM) experiments are now sufficiently sensitive to be able to detect some structure in individual C₆₀ molecules and anions, both on surfaces and in monolayers.

In general, any system with a partially filled set of degenerate levels will be subject to the Jahn-Teller (JT) effect, where coupling between electronic and vibrational motion results in an instantaneous energy-lowering distortion. Strong JT effects are present in C₆₀ ions, which has a strong effect on many observed physical properties. The JT effect in an isolated fullerene anion causes an instantaneous distortion to a lower symmetry. However, as there are multiple distorted configurations with the same energy, quantum-mechanical tunnelling between these configurations means that the overall symmetry will still be icosahedral, and the JT effect is said to be dynamic. However, when C₆₀ ions are adsorbed onto a surface, the interactions with the surface could induce a static distortion. Also, when multiple ions interact (electronically, magnetically or via spin, for example) the co-operative JT effect can lead to non-zero static distortions at low temperatures. Whilst it is clear that the JT effect plays an important part in all these systems, the precise role of the JT effect is far from clear and many questions remain unanswered. The aim of this proposal is to probe the nature of the JT effect in fullerene anions when formed into a monolayer and / or adsorbed onto a surface in order to explain the results of experiments on these systems available from the literature.

The work will be a mixture of analytical and computational calculations. It will be carried out in the research group of Dr Janette Dunn, who is a member of the theoretical physics group at the University of Nottingham (see http://www.nottingham.ac.uk/~ppzkab/Theory/nano.html). The work also has the support of the Nottingham Nanoscience group, who are internationally respected for their work on STM and surface science and will be able to provide valuable experience in this area. It is possible that some collaboration with this group may take place in the later stages of the project. However, it should be noted that this project is a theoretical one. It will involve the analysis of published data, but will not involve taking any new data.

The candidate must have a PhD in Physics or a related discipline (e.g. theoretical chemistry). We anticipate that applicants may either have experience in the Jahn-Teller effect and wish to learn more about surface science / nanostructures, or alternatively they may have experience in surface science and wish to learn about the Jahn-Teller effect. However, whilst experience in one (or more) of these areas is desirable, it is not essential. In addition, suitable candidates will either be theoreticians or will be able to demonstate a past record that includes a reasonable amount of theory.

Details of the post

Salary will be within the range £21,467 - £30,606 per annum, depending on qualifications and experience (salary can progress to £34,448 per annum, subject to performance).

This post will be offered on a fixed-term contract for a period of up to three years, depending on qualifications and experience.

Informal enquiries may be addressed to Dr Janette Dunn, Email: Janette.Dunn@Nottingham.ac.uk.

Applications should be made by sending a detailed CV, a brief description of your research interests and the names and addresses of two referees, to

Melanie Stretton,
School of Physics & Astronomy,
University of Nottingham,
University Park,
Nottingham,
NG7 2RD,
UK

Tel:+44 (0)115 951 5183. Fax: :+44 (0)115 846 6070.

Email: Melanie.Stretton@Nottingham.ac.uk.

The closing date is Friday 12th January 2007. It is expected that interviews will be held in February with a start date of 1st March 2007 or as soon as possible thereafter.