1. Los Alamos National Laboratory
Artificial Spin Ice: From Toy to Material by Design?
Cristiano Nisoli
Los Alamos National Laboratory

2. Frustration
Frustration:
a set of constraints not all of which can be satisfied at the same time

3. Frustration
Frustration:
a set of constraints not all of which can be satisfied at the same time
Compromises:
Attempt to optimize gains vs. sacrifices

4. Frustration
Frustration:
a set of constraints not all of which can be satisfied at the same time
Compromises:
Attempt to optimize gains vs. sacrifices
Manifold of Choices
Something between order and disorder

5. Geometric Frustration
Interesting because…
The collective and correlated local compromises compose into a degenerate ensemble that is disordered (extensive entropy) yet not random.
Order is boring. Randomness is death. Life happens somewhere in between. Life needs susceptibility, response.

6. Geometric Frustration
G. H. Wannier Phys. Rev. 79, 357 (1950)

7. Ice Rule in Water Ice and Spin Ice

8. Ice Rule in Water Ice and Spin Ice

9. Ice Rule in Water Ice and Spin Ice

10. Ice Rule in Water Ice and Spin Ice

11. Monopoles

12. Monopoles

13. Monopoles

14. Ice Rule in Water Ice and Spin Ice
"Magnetic monopoles in spin ice." Nature (2008):

15. Ice Rule in Water Ice and Spin Ice
"Measurement of the charge and current of magnetic monopoles in spin ice." Nature (2009):
"Magnetic monopoles in spin ice." Nature (2008):

16. Reviews of Modern Physics 85 (4), 1473 (2013)
Artificial Spin Ice: Interacting Magnetic Nanoislands
Direct Imaging of magnetic degrees of freedom
Designing the low energy dynamics for the collective behavior of interacting nanostructures
Nature 439, (2006)
Reviews of Modern Physics 85 (4), 1473 (2013)

17. Out of equilibrium statistical mechanics
Artificial Spin Ice: Early Fun
Out of equilibrium statistical mechanics
Possibility to test directly a theoretical framework
Phys. Rev. Lett. 98 (21), (2007)
Phys. Rev. Lett. 105, (2010)

18. Out of equilibrium statistical mechanics
Artificial Spin Ice: Early Fun
Out of equilibrium statistical mechanics
Possibility to test directly a theoretical framework
Phys. Rev. Lett. 98 (21), (2007)
Phys. Rev. Lett. 105, (2010)

19. ASI Developing into a multidisciplinary field
Hexagonal Geometry: extensive degeneracy Phys. Rev. B 73, , 2006 Phys. Rev. B 77, , 2008

20. ASI Developing into a multidisciplinary field
Hexagonal Geometry: extensive degeneracy Phys. Rev. B 73, , Phys. Rev. B 77, , 2008
Field Reversal and monopole imaging Nature Physics 6, 359, 2010 Nature Physics 7, 68, 2011

21. ASI Developing into a multidisciplinary field
Hexagonal Geometry: extensive degeneracy Phys. Rev. B 73, , 2006 Phys. Rev. B 77, , 2008
Field Reversal and monopole imaging Nature Physics 6, 359, 2010 Nature Physics 7, 68, 2011
Direct Extraction of Entropy/Shannon Information theory Nature Physics 6, 786, 2010

22. Topological Hall Effect Science 335, 1597, 2012
ASI Developing into a multidisciplinary field
Hexagonal Geometry: extensive degeneracy Phys. Rev. B 73, , 2006 Phys. Rev. B 77, , 2008
Field Reversal and monopole imaging Nature Physics 6, 359, 2010 Nature Physics 7, 68, 2011
Direct Extraction of Entropy/Shannon Information theory Nature Physics 6, 786, 2010
Topological Hall Effect Science 335, 1597, 2012

23. Thermal ensembles
Nature Physics 7, 75, 2011
New J. Phys. 14, , 2012

24. Artificial Spin ice, Emergence, Subtle Exotic States
Nature 500, 553–
However it became clear that higher level of controls were necessary to reveal emergence. The problem was solved in when we developed new protocols capable to reach lower entropy states of these materials, and access new emergent phenomena.
This meant that my job had to change. The material was now mature to go from descriptive science to design science and hypothesis-driven design and research.
Phys. Rev. Lett. 106,
New J. Phys

25. Geometric Frustration
G. H. Wannier Phys. Rev. 79, 357 (1950)

26. New Theoretical Directions: DESIGNING EMERGENCE
That is what finally convinced me that the material could be used not only to access delicate exotic states, but to design them. My job had changed. It was not to make more vague proposal for realization and then explain the results in a situation where so many variables were unforeseeable. Now the doors to emergence by design were open. This is more rewarding but also more risky. We started

27. New Theoretical Directions: DESIGNING EMERGENCE
That is what finally convinced me that the material could be used not only to access delicate exotic states, but to design them. My job had changed. It was not to make more vague proposal for realization and then explain the results in a situation where so many variables were unforeseeable. Now the doors to emergence by design were open. This is more rewarding but also more risky. We started

28. New Journal of Physics 15 (4), 045009 2013
New Theoretical Directions: DESIGNING EMERGENCE
That is what finally convinced me that the material could be used not only to access delicate exotic states, but to design them. My job had changed. It was not to make more vague proposal for realization and then explain the results in a situation where so many variables were unforeseeable. Now the doors to emergence by design were open. This is more rewarding but also more risky. We started
New Journal of Physics 15 (4),

29. New Theoretical Directions: DESIGNING EMERGENCE
That is what finally convinced me that the material could be used not only to access delicate exotic states, but to design them. My job had changed. It was not to make more vague proposal for realization and then explain the results in a situation where so many variables were unforeseeable. Now the doors to emergence by design were open. This is more rewarding but also more risky. We started

30. New Theoretical Directions: DESIGNING EMERGENCE
That is what finally convinced me that the material could be used not only to access delicate exotic states, but to design them. My job had changed. It was not to make more vague proposal for realization and then explain the results in a situation where so many variables were unforeseeable. Now the doors to emergence by design were open. This is more rewarding but also more risky. We started

31. New Theoretical Directions: DESIGNING EMERGENCE
Physical Review Letters 111,

32. New Theoretical Directions: DESIGNING EMERGENCE
Nature Physics 10, 670–675 (2014)

33. New Theoretical Directions: DESIGNING EMERGENCE
Nature Physics 10, 670–675 (2014)

34. New Theoretical Directions: DESIGNING EMERGENCE

35. New Theoretical Directions: DESIGNING EMERGENCE

36. New Theoretical Directions: DESIGNING EMERGENCE
Nature Physics, under review

37. New Theoretical Directions: DESIGNING EMERGENCE

38. New Theoretical Directions: DESIGNING EMERGENCE

39. Conclusions
Artificial spin ice was introduced initially to mimic the frustration of spin ice and to realize celebrated model of statistical mechanics
It became a fruitful ground to study diverse novel phenomena and exotic states
Advances in control and manufacturing have opened the way to a material-by-design in magnetism
Useful or exotic magnets are rare and found serendipitously in nature. They are based on localized, dipolar degrees of freedom. Emergent properties are at low T
New materials based on delocalized, monopolar degrees of freedom could be a game changer for high T emergence
The field is now mature for designing emergence

40. Collaborators Peter Schiffer UI Urbana Ian Gilbert NIST
Sheng Zhang Argonne
Vincent Crespi Penn State
Paul Lammert Penn State
Gia-Wei Chern LANL
Muir Morrison Caltech
Tammie Nelson LANL