Thursday, January 03, 2008

Magnetic Monopoles in Spin Ice?

When I wrote about the Kondo effect a while back, I mentioned that there were many fundamental physics that came out of the field of condensed matter, one of them being the inspiration for the Higgs mechanism.

Now comes another theoretical discovery from condensed matter that could shed light on the on-going search for the magnetic monopoles. It appears that such a thing could be found in, of all places, a magnetic material called the spin ice. Again, just like the fractional quantum hall system, the dimensional effect in a strongly-correlated electron system can produce such a rich set of phenomena, it is just a zoo of basic, fundamental physics waiting to be discovered.

This paper has been published in Nature[1]. Also don't miss the News and Views review of this paper by Oleg Tchernyshyov in the same issue of Nature.

One environment in which monopoles might pop up is crystalline solids. In a crystal at a low temperature, excitations above the ground state often behave like elementary particles: they carry a quantized amount of energy, momentum, electric charge and spin. In their theoretical study, Castelnovo et al. find the first instance of such an excitation with a non-zero magnetic charge. Under certain conditions, these magnets behave as a gas of independent magnetic poles. There is even a phase transition at which a thin vapour of these monopoles condenses into a dense liquid.

Moral of the story: you CAN study some of the most fundamental aspect of our world in Condensed matter physics. It is as fundamental as any. Just because the field has a direct application to the study of the properties of materials doesn't make it any less fundamental.


[1] C. Castelnovo et al, Nature v.451, p.42 (2008).

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