Water Ice and Spin Ice: Ground States and Topological Defects

Prof. John Cumings, University of Maryland College Park
Deepak K. Singh

Our planet is called Earth, but based on the surface composition, perhaps it should have been called Water. Despite the ubiquitous presence on our planet, water's solid form, ice does not readily enter the ground state upon cooling, owing to residual disorder of the hydrogen atoms in the lattice. In the 1990s, a class of magnetic ceramic materials was discovered, with similar behavior of its magnetic moments as the protons in ice, and these materials came to be known as Spin Ice. In a cleanroom facility, researchers today can design nanoscale magnetic latticework structures that mimic the behavior of spin ices and water ices, with the advantage that the interactions and behavior can be controlled by design. Such materials are known as Artificial Spin Ice, and I will present work on the behavior of these materials when intentional defects are programmed into the latticework. These artificial defects mimic the real defects that are known to occur in a wide range of materials, including water ice and the ceramics phases that play host to the spin ices. The implications for other ground state phases, such as high temperature superconductors, will be discussed.

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