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Home > Physics home > Research > Postgraduate Opportunities > Condensed Matter Physics > Controlling strongly correlated electrons in sodium cobaltate
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Controlling strongly correlated electrons in sodium cobaltate

 x-ray diffraction experiment x-ray diffraction calculation 
 X-Ray Diffraction Experiment
 X-Ray Diffraction Calculation

 superstructure  Coulomb landscape
 Superstructure  Coulomb landscape

Sodium cobaltate (NaxCoO2) has emerged as a material of exceptional scientific interest due to the potential for thermoelectric applications, and because the strong interplay between the magnetic and superconducting properties has led to close comparisons with the physics of the superconducting copper oxides. We have shown by diffraction that the sodium ordering and its associated distortion field are governed by pure electrostatics, and that the organisational principle is the stabilisation of charge droplets that order long range at some simple fractional fillings [1].

Our results provide a good starting point to understand the electronic properties in terms of a modified Hubbard Hamiltonian that takes into account the electrostatic potential, or “Coulomb landscape”, in the cobalt layers from the superstructures. The resulting depth of potential wells in the Co layer is greater than the single-particle hopping kinetic energy and, as a consequence, holes preferentially occupy the lowest potential regions. In this way we are able to control the strongly correlated electron behaviour, predict magnetic structures, transport properties, etc.

The following PhD projects are currently available focusing on the following areas:

  1. Synthesis of single crystals and thin films of new thermoelectric oxides.
  2. Thermoelectric and transport properties.
  3. Superstructure determination using x-ray and neutron diffraction.
  4. Measurement of magnetic ordering using polarised neutron scattering.
  5. Measurement of charge ordering using resonant x-ray scattering.

[1] M. Roger, D.J.P. Morris, D.A. Tennant, M.J. Gutmann, J.P. Goff, J.-U. Hoffmann, R. Feyerherm, E. Didzik, D. Prabhakaran, A. T. Boothroyd, N. Shannon, B. Lake and P.P. Deen, Nature 445, 631 (2007).

For further information contact Professor Jon Goff.


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