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Reference : UMR5672-PETHOL-001
Workplace : LYON 07
Date of publication : Friday, September 10, 2021
Scientific Responsible name : Peter Holdsworth
Type of Contract : PhD Student contract / Thesis offer
Contract Period : 36 months
Start date of the thesis : 1 October 2021
Proportion of work : Full time
Remuneration : 2 135,00 € gross monthly
Description of the thesis topic
The quasi particle excitations of the frustrated magnets known as spin ice are topological defects carrying magnetic charge – magnetic monopoles [1,2], solid state analogues of the elusive fundamental particles predicted by Dirac almost a century ago . The magnetic moments of spin ice hence map onto elements of an effective electromagnetic field [4,5] making an experimentally relevant generator of emergent electromagnetism. Remarkably, the field “fragments” [4,5] into distinct divergence full and divergence free parts via a Helmholtz decomposition. This emergent two component system yields an extensive phase diagram, rich in thermodynamic and topological properties [6,7].
In this theoretical and numerical project, we will explore the recently established phase diagram [6,7]. Two particular directions of study will be the stability of the phase diagram in the presence of disorder and the three-dimensional topological phase transitions characteristic of the emergent electromagnetic picture. Both questions are highly relevant for experiment and linked to intensive experimental programs in place in Grenoble and elsewhere.
The project is ideally suited to students motivated by numerical methods but who wish to remain close to the fundamental science. The first axis of study will require high performance methods to deal with long range (Coulomb) interactions and disorder, while the second will require the development of non-local (loop) algorithms adapted to topological questions. Collaborations will initially be with groups in Grenoble, in Argentina and in the United Kingdom.
1] Castelnovo, C., Moessner, R. & Sondhi S.. Nature 451, 42-45 (2008).
 L. Jaubert and P. C. W. Holdsworth, Nature Physics 5, 258
- 261 (2009).
 P. A. M. Dirac, Proc. R. Soc. A133, 60, (1931).
 M. E. Brooks-Bartlett, S. T. Banks, L. D. C. Jaubert, A. Harman-Clarke, and P. C. W. Holdsworth. Phys. Rev. X, 4:011007, Jan 2014.
 Elsa Lhotel, Ludovic D. C. Jaubert and Peter C. W. Holdsworth, , J. Low. Temp.
 V. Raban, C.T. Suen, L. Berthier, P.C.W. Holdsworth, Phys. Rev. B 99,
 V. Cathelin et. Al., arXiv:2005.08807, Phys. Rev. Res. (2020).
The thesis is financed by ANR grant No. ANR-19-CE30-0040 (FRAGMENT), a theory - experiment collaboration between LPENSL, Laboratoire Neel à Grenoble and LLB Saclay.
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