Is a superconductor nearly a spin liquid insulator? (Ben Powell)
Tue, 05/26/2009 - 10:20 — adminImagine that we are having a dinner party. We have decided to seat our guests around a table so that each person has a member of the opposite sex on either side of them. If I have a square table and four guests this is not difficult. However, if we have a triangular table and three guests it is impossible. In an antiferromagnet the electrons want to sit with their spins pointing in the opposite direction to their neighbours. Again this is straightforward to arrange on a square lattice but impossible to achieve on the triangular lattice. This effect is known as frustration....Read more
Can density functional theory describe the Mott insulator? (Ben Powell)
Tue, 05/26/2009 - 11:39 — adminDensity functional theory (DFT) is one of the most computationally tractable methods of solving the Schrödinger equation for atoms, molecules, and solids. It is such a valuable tool in theoretical chemistry and solid state physics that Walter Kohn and John Pople shared Nobel Prize for developing it. Yet there are many situations where DFT does not work well [1]. One of the most important of these situations is when the interactions and hence the correlations between electrons are strong....Read more
The renormalisation group for quantum chemistry (Ben Powell)
Tue, 05/26/2009 - 13:21 — adminWilson’s renormalisation group is often regarded as the most important idea in physics from the second half of the twentieth century. It has had profound influence in fields as disparate as condensed matter physics and high-energy particle physics. One of the key ideas of the renormalisation group is that rather than study the full Hamiltonian of the system of interest, which is usually intractable, one should study an effective low energy Hamiltonian. An effective Hamiltonian is derived by ‘integrating out’ the high-energy degrees of freedom of the system....Read more
Quantum Chemistry of Molecules for Organic Solar Cells (Ben Powell)
Tue, 05/26/2009 - 13:26 — adminEveryone knows that climate change and the cost/availability of fossil fuel are going to change the way that mankind produces and uses energy. Organic solar cells are seen as a lead "next generation" solar cell technology and will undoubtedly have a significant role in the future energy mix. In the Centre for Organic Photonics and Electronics (COPE) we design and synthesise new materials for photon harvesting in organic solar cells. We also fabricate and test prototype devices in state-of-the-art clean room facilities....Read more
Dimensionless ratios in condensed matter physics (Ben Powell)
Tue, 05/26/2009 - 13:29 — adminDeep physical insights have come from studying ratios of measured quantities that take universal values, which depend on only fundamental constants. Examples of universal ratios include the Wiedemann-Franz, Sommerfeld-Wilson, Kadowaki-Woods and Korringa ratios. Materials that violate these laws have provided particular insight into, non-Fermi liquids, strong electronic correlations, and magnetic fluctuations....Read more
Gauge fluctuations in organic superconductors (Ben Powell; PhD only)
Tue, 05/26/2009 - 14:14 — adminThis project will investigate a simple question: why does superconductivity disappear as we raise the temperature? To understand this question one needs to understand that two ingredients are required for superconductivity (i) the electrons must pair up into “Cooper pairs” to overcome the Pauli exclusion principle and (ii) long-range phase coherence must exist between the Copper pairs, i.e. the wavefunction must have the same phase in macroscopically separated parts of the sample....Read more
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New Scholarship available
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Positions Vacant There are currently five Postdoctoral Research Fellow positions available in the Centre: Postdoctoral Research Fellow - Organic Photovoltaics (four positions) Postdoctoral Research Fellow - Light-emitting dendrimer synthesis (one position)
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