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
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.
We are working with collaborators in Dresden, Lausanne, Brookhaven and elsewhere, to investigate electronic ordering and dynamics in antiferromagnets, including layered nickelates, cobaltates and manganites, and rare-earth iron garnets.
Prof. Andrew Boothroyd
Clarendon Laboratory
Oxford, OX1 3PU
United Kingdom
phone
+44 (0) 1865 272376
fax
+44 (0) 1865 272400
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 12 (2013) 1028–1032 [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 nickelates, manganites and cobaltates, and rare-earth iron garnets. 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:
Charge Condensation and Lattice Coupling Drives Stripe Formation in Nickelates
Y. Shen, G. Fabbris, H. Miao, Y. Cao, D. Meyers, D. G. Mazzone, T. A. Assefa, X. M. Chen, K. Kisslinger, D. Prabhakaran, A. T. Boothroyd, J. M. Tranquada, W. Hu, A. M. Barbour, S. B. Wilkins, C. Mazzoli, I. K. Robinson, and M. P. M. Dean
Phys. Rev. Lett. 126 (2021) 177601 (arXiv:2104.00082)
The full magnon spectrum of yttrium iron garnet
A. J. Princep, R. A. Ewings, S. Ward, S. Tóth, C. Dubs, D. Prabhakaran and A. T. Boothroyd
npj Quantum Materials 2 (2017) 63 (open access) (arXiv:1705.06594)
G. Fabbris, D. Meyers, L. Xu, V. M. Katukuri, L. Hozoi, X. Liu, Z.-Y. Chen, J. Okamoto, T. Schmitt, A. Uldry, B. Delley, G. D. Gu, D. Prabhakaran, A. T. Boothroyd, J. van den Brink, D. J. Huang, and M. P. M. Dean
Phys. Rev. Lett. 118 (2017) 156402 (arXiv:1612.06903)
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)
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.
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).
