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Ben Powell

Condensed Matter Physics | COPE | Physics | SPS | EPSA | University of Queensland
postdocs | students | collaborators | organic superconductors | magnets | model parameters | biophysics
glasses (radio interview)
PHYS2020 (Thermodynamics and CMP) | Quantum Many-Body Theory reading group
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BEN POWELL

Research

Students

I am currently supervising the following students:

Ph.D.

[There should be a photo here.] Anthony Jacko Co-supervisor (2007-present), strong correlations in organo-metallic materials
[There should be a photo here.] Bernard Mostert Associate supervisor (2007-present), electrical properties and spin dynamics in melanins and related materials
[There should be a photo here.] Edan Scriven Principal supervisor (2006-present), organic superconductors, DFT, Hubbard models
[There should be a photo here.] Andrew Stephenson Principal supervisor (2006-present), plastic superconductors


I am always interested in taking on talented research students (for Ph.D., M.Sc., honours or summer projects). Please contact me for further details.


Former postdocs

[There should be a photo here.] Ujjual Divakar (2006-2008), plastic superconductors
Eddy Yusuf (2005-2007), organic superconductors, pseudogap phenomena

Former students

Including electronic copies of the student's theses where available.

Ph.D.

[There should be a photo here.] Jenny Riesz Associate supervisor (Queensland, 2004-2007) Spectroscopic properties of melanins

Masters

[There should be a photo here.] Johannes de Boor Associate supervisor (Queensland, 2007) Charge Transport in eumelanin
[There should be a photo here.] Michael Deceglie Associate supervisor (Queensland, 2006-2007) Novel hydrophobic dendritic sensitisers for use in dye-sensitised solar cells: the effect of molecular structure on performance and charge transfer dynamics

Honours (final year undergraduate)

[There should be a photo here.] Anthony Jacko Principal supervisor (Queensland, 2006, first class honours) Non-Universality of the Kadowaki-Woods Ratio in Layered Materials
[There should be a photo here.] Bernard Mostert Associate supervisor (Queensland, 2006, first class honours in Chemistry), Proton conduction in Bio-macromolecules
Greg Freebairn Principal supervisor (Queensland, 2005, first class honours and a University Medal) Phonons and the Isotopically Induced Mott transition
[There should be a photo here.] Clare Giacomantonio Associate supervisor (Queensland, 2004-5, first class honours and a University Medal) Charge Transport in Melanin, a Disordered Bio-Organic Conductor

Summer undergraduate projects

John Varghese (2005-6)
Antony Jacko (2005-6)
Greg Freebairn (2004-5)
Andrew Dennis (2003-4)

Collaborators

I am a member of the condensed matter physics group and the centre for organic photonics and electronics (COPE). There are three other members of staff working on condensed matter physics John Fjaerestad (theory), Ross McKenzie (theory) and Paul Meredith (experiment). My interests strongly overlap with their's and we collaborate frequently. Some of my other more frequent collaborators are:

James Annett (Bristol) - triplet superconductivity, ferromagnetic superconductors, BCS-BEC crossover
Arzhang Ardavan (Oxford) - organic superconductors
Steve Blundell (Oxford) - organic superconductors, theory of muSR
Bill David (RAL) - organic superconductors, calculation of parameters of simple models
Brad Marston (Brown) - RVB theory, organic superconductors, frustrated antiferromagnets
Jaime Merino (UAM) - NaxCoO2, calculation of parameters of simple models
Adam Micolich (UNSW) - soft solids, biophysics, melanin
Mark Pederson (NRL) - DFT, calculation of parameters of simple models, melanin
Francis Pratt (RAL) - organic superconductors, theory of muSR
Jorge Quintanilla (RAL) - Pomeranchuk instabilities

Layered organic superconductors: from quantum chemistry to quantum many-body physics to experiment

My primary interests are unconventional superconductivity and the interplay of superconductivity with magnetism. I am currently working on the layered organic superconductors. I have carried out two analyses of the experimental constraints on our knowledge of the superconducting state. My study of the role of disorder suggested that the pairing symmetry in these materials is likely to be d-wave, however, some loopholes still exist. I am therefore working with several groups of experimentalist to close these loopholes by performing experiments which I have designed. I am, with Kevin Brake and Ross McKenzie, performing ab initio calculations to understand the mechanism for cooling rate induced disorder. My study of the penetration depth of the layered organic superconductors showed that the superconductivity in these materials cannot be explained by either BCS theory by the theory of Kosterlitz--Thouless phase transitions.

Quantum many-body theory of layered organic superconductors and frustrated antiferromagnets

Therefore I am currently working on an RVB theory of these materials to discover whether it is compatible with the measured penetration depth. I have a collaboration with Francis Pratt (Rutherford Appleton Laboratory - RAL) to test the predictions of these calculations. I am also working on the RVB theory for frustrated Heisenberg antiferromagnets in collaboration with John Paul Barjaktarevic. We also have a close experimental collaboration with Radu Coldea to both apply our results to his experiments and the test the predictions of our theory.

Calculation of the parameters of simple quantum many-body models of strongly correlated materials from first principles quantum chemistry

The Hubbard model is has been proposed as a minimal model for the layered organics superconductors. I am also working, with Kevin Brake and Ross McKenzie, to calculate the parameters of this model from first principles. This will provide an extremely stringent test of the applicability of the model to these systems and input the parameter values for my RVB theory. To perform these calculations requires both significant technical knowhow of first principles calculations for which I have a collaboration with the group of Mark Pederson (Naval Research Laboratory, Washington D.C. - NRL) and the input of the state of the art neutron diffraction experiments, for which I am collaborating with one of the world's leading crystallographers, Bill David (RAL).

Computational biophysics and molecular engineering

I am also interested in a class of biological materials known as the eumelanins. These are the primary photoprotectant in man an it is also possible that they are a naturally occurring soft-solid semiconductor. In close collaboration with Paul Meredith's experimental group at UQ and Mark Pederson's group at NRL I am investigating the properties of these molecules via first principles calculations. Our goal is to understand the structure-property-function relationships of these materials using a bottom up approach and working closely with experimentalists.