Exploring Emergent Phenomena in Artificial Frustrated Systems

08.05.2018 13:00 – 14:30

Frustrated magnetism offers a variety of lattice geometries where interactions between magnetic
moments cannot be simultaneously satisfied1-3. Pyrochlore spin ice2 provided a prototypical
example of the consequences of geometrical frustration with a highly debated zero-point
entropy4,5, which was successfully described using the concept of emergent magnetic charges.
Artificial spin ice, consisting of dipolar coupled Ising-type nanomagnets, lithographically
arranged onto a two-dimensional square lattice6,7, was introduced as a two-dimensional analogue
to pyrochlore spin ice and provided the prospect to microscopic studies on the consequence of
geometrical frustration. In my presentation, I will give an overview on my most recent research
activities, ranging from exploring polaronic states in a two-dimensional dipolar dice lattice8, the
introduction of novel concepts of two-dimensional artificial frustrated systems9,10 and efforts in
generating macroscopically degenerate artificial square ice11,12 patterns and investigating their
real-time thermodynamics.

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the ternary solid solution between CoSb and Fe1+dSb. Physical Review B 77, 144405 (2008).
2 Harris, M. J., Bramwell, S. T., McMorrow, D. F., Zeiske, T. & Godfrey, K. W. Geometrical
frustration in the ferromagnetic pyrochlore Ho2Ti2O7. Physical review letters 79, 2554-2557,
doi:DOI 10.1103/PhysRevLett.79.2554 (1997).
3 Helton, J. S. et al. Spin dynamics of the spin-1/2 kagome lattice antiferromagnet ZnCu3(OH)6Cl2.
Physical review letters 98, 107204 (2007).
4 Pomaranski, D. et al. Absence of Pauling/'s residual entropy in thermally equilibrated Dy2Ti2O7.
Nat Phys 9, 353-356, doi:10.1038/nphys2591 (2013).
5 Ramirez, A. P., Hayashi, A., Cava, R. J., Siddharthan, R. & Shastry, B. S. Zero-point entropy in 'spin
ice'. Nature 399, 333-335 (1999).
6 Farhan, A. et al. Direct observation of thermal relaxation in artificial spin ice. Physical review
letters 111, 057204 (2013).
7 Wang, R. F. et al. Artificial 'spin ice' in a geometrically frustrated lattice of nanoscale
ferromagnetic islands. Nature 439, 303-306, doi:Doi 10.1038/Nature04447 (2006).
8 Farhan, A. et al. Thermodynamics of emergent magnetic charge screening in artificial spin ice.
Nat Commun 7, 12635, doi:10.1038/ncomms12635 (2016).
9 Farhan, A. et al. Nanoscale control of competing interactions and geometrical frustration in a
dipolar trident lattice. Nature Communications 8, 995, doi:10.1038/s41467-017-01238-4 (2017).
10 Petersen, C. F. et al. Tuning magnetic ordering in a dipolar square-kite tessellation. Applied
Physics Letters 112, 092403, doi:10.1063/1.5014041 (2018).
11 Möller, G. & Moessner, R. Artificial Square Ice and Related Dipolar Nanoarrays. Physical review
letters 96, 237202 (2006).
12 Perrin, Y., Canals, B. & Rougemaille, N. Extensive degeneracy, Coulomb phase and magnetic
monopoles in artificial square ice. Nature 540, 410-413, doi:10.1038/nature20155 (2016).

Lieu

Bâtiment: Ecole de Physique

auditoire Stuckelberg

Organisé par

Faculté des sciences
Département de physique de la matière quantique

Intervenant-e-s

Alan Farhan, Paul Scherrer Institute

entrée libre

Classement

Catégorie: Séminaire