Our research

The interactions between electrons in solids are responsible for a large number of exciting physical phenomena, including ferromagnetism, antiferromagnetism and superconductivity. In these materials, we cannot treat the electrons as independent entities but have to consider their correlated behaviour. Understanding electron-electron interactions in a variety of systems, including transition metal oxides and organic molecular solids, is a central part of our research.

For enquiries about the group, please contact: Professor Stephen Blundell (group leader), s.blundell@physics.ox.ac.uk Dr Arzhang Ardavan (group leader), a.ardavan@physics.ox.ac.uk

Latest news

Twenty years of ISIS muons! The muon beamlines at the nearby ISIS facility are celebrating their 20th birthday.

Recent results

Electrons order themselves in the charge-ordered triangular antiferromagnet AgNiO₂

The triangular lattice of nickel ions that forms the antiferromagnet AgNiO2 prevents this material from finding a unique ground state of both spin and orbital angular momentum. We have used implanted muons to show that this may cause AgNiO2 to adopt an exotic "charge ordered" state, where electrons arrange themselves on the nickel ions in a periodic pattern. Our results, which are of unprecedented resolution, show a highly unusual dependence on temperature and suggest that this new state of condensed matter still has much to reveal.

Anomalous temperature evolution of the internal magnetic field distribution in the charge-ordered triangular antiferromagnet AgNiO₂

T. Lancaster, S. J. Blundell, P. J. Baker, M. L. Brooks, W. Hayes, F. L. Pratt, R. Coldea, T. Soergel and M. Jansen,
Phys. Rev. Lett. 100, 017206 (2008) Link

Entangling muon and fluorine moments in molecular magnets

We have exploited quantum entanglement to probe the surroundings of muons in matter. The muon, a type of subatomic particle, is often implanted into materials to probe the internal magnetic fields. In the past, such studies have been criticised since the exact environment of the muon is often mysterious. Our work, which exploits the quantum mechanical interaction of the muon and the nuclei of fluorine atoms, allows us to identify the atomic surroundings of the muon. We also suggest ways to trap muons in known configurations allowing muons studies access to new information.

Muon-Fluorine Entangled States in Molecular Magnets

T. Lancaster, S. J. Blundell, P. J. Baker, M. L. Brooks, W. Hayes, F. L. Pratt, J. L. Manson, M. M. Conner, and J. A. Schlueter,
Phys. Rev. Lett. 99, 267601 (2007) Link

Electrons' love-hate relationship breeds superconducting apparition

In a Letter to Nature published this week, scientists in Oxford report that a form of shimmering superconductivity exists at temperatures well above that at which ordinary superconductivity is destroyed. This effect is caused by the tension between the conflicting urges for electrons to pair up (which leads to superconductivity) and to repel each other (which leads to insulating behaviour). The effect has been discovered in a molecular superconductor which is close to the border between superconducting and insulating behaviour so that the tension produced by the electrons' love-hate relationship is most acute: near this border the electrons cannot decide whether to pair up or remain single. If the preference for love very slightly exceeds hate, then it is possible for them to exhibit the shadowy state of fluctuating superconductivity. More information.

Fluctuating superconductivity in organic molecular metals close to the Mott transition

Moon-Sun Nam, Arzhang Ardavan, Stephen J. Blundell, and John A. Schlueter,
Nature 449, 584 (2007) Link

Nanoscale magnets show new promise as quantum information processors

Together with collaborators at the Universities of Manchester and Princeton, we have moved a step closer to making a new kind of information processing device called a quantum computer by using tiny magnets, each one made out of a single molecule. In a quantum computer, the information-carrying elements are permitted to exist in strange quantum states, known as qubits. Our results show that the time for which the qubits can be stable can significantly exceed the time it takes to perform operations on them. This is the crucial prerequisite for the deployment of these systems in quantum information applications. More information.

Will spin-relaxation times in molecular magnets permit quantum information processing?

Arzhang Ardavan, Olivier Rival, John J.L. Morton, Stephen J. Blundell, Alexei M. Tyryshkin, Grigore A. Timco, and Richard E.P. Winnpenny,
Phys. Rev. Lett. 98, 057201 (2007) Link