Research
 

Complex electronic order

The physical properties of systems of strongly correlated electrons can be strongly influenced by the coupling between different degrees of freedom, e.g. spin, charge, orbital and lattice. If several different types of interaction are present and of a similar energy then it can lead to competing ground states, with many different phases often involving complex forms of electronic order. A small external stimulus can cause a strong response in the system.

 

Current projects

  • Superstructures and control of electrons

    This project was undertaken in collaboration with Prof Jon Goff (Royal Holloway, University of London), funded by EPSRC grant EP/J012912/1, The control of electrons through patterning of superstructures.

  • Spin and charge order in transition-metal oxides

    We are working with collaborators in Dresden, Lausanne, Brookhaven and elsewhere, to investigate electronic ordering in doped antiferromagnets, including layered cobaltates and manganites.

     

  • Prof. Andrew Boothroyd

    Clarendon Laboratory

    Department of Physics

    Oxford University

    Oxford, OX1 3PU

    United Kingdom

    phone

     +44 (0) 1865 272376

    fax

    +44 (0) 1865 272400

    a.boothroyd@physics.ox.ac.uk

     

     

    Home

    People

    Research

    Publications

    Software

    Teaching

    News

    Links

     
     
       

    Superstructures and control of electrons

    We are studying the effect of Na superstructures on the physical properties of NaxCoO2, and related materials. For more details of this work, see,

    Suppression of thermal conductivity by rattling modes in thermoelectric sodium cobaltate

    D. J. Voneshen, K. Refson, E. Borissenko, M. Krisch, A. Bosak, A. Piovano, E. Cemal, M. Enderle, M. J. Gutmann, M. Hoesch, M. Roger, L. Gannon, A. T. Boothroyd, S. Uthayakumar, D. G. Porter and J. P. Goff

    Nature Materials DOI: 10.1038/nmat3739.

     

    Spin and charge order in transition-metal oxides

    We have used neutron inelastic scattering to investigate the characteristic magnetic excitation spectrum of spin and charge ordered antiferromagnets, including layered manganites and cobaltates. The spectrum of a half-doped manganite was analysed to show that the ground state is well described by Goodenough's CE model. In the La2-xSrxCoO4 system we have found evidence for charge stripes and observed an hourglass spectrum which is qualitatively similar to that found in the copper oxide superconductors.

    For more details of this work, see:

    Ground State in a Half-Doped Manganite Distinguished by Neutron Spectroscopy

    G. E. Johnstone, T. G. Perring, O. Sikora, D. Prabhakaran, and A.T. Boothroyd

    Phys. Rev. Lett. 109 (2012) 237202.

    An hour-glass magnetic spectrum in an insulating, hole-doped antiferromagnet

    A. T. Boothroyd, P. Babkevich, D. Prabhakaran, and P. G. Freeman

    Nature 471 (2011) 341–344.

    Direct evidence for charge stripes in a layered cobalt oxide

    P. Babkevich, P. G. Freeman, M. Enderle, D. Prabhakaran, and A. T. Boothroyd

    Nat. Commun. 7 (2016) 11632 doi: 10.1038/ncomms11632 (open access)

    Facilities and Equipment in the Group

    Most of this work employs large single crystals grown from the melt by the floating-zone method in an image furnace.

     

    Magnetic structure of NaxCoO2

     

     

    Spin excitation spectrum of the half-doped manganite PCSMO. Measurements (upper) and simulation (lower).