I understand the significance to physics, but what can a magnetic monopole be used for assuming we could free them from spin ice and put them to work? What would be a magnetic version of electricity?
EDIT
Sorry this wasn't clear. The question is mixed between the quasiparticle and the theoretical elementary particle based on some similarities between the two. I am more interested in the quasiparticle and if they have properties in some way that are similar to particle version:
There are a number of examples in condensed-matter physics where
collective behavior leads to emergent phenomena that resemble magnetic
monopoles in certain respects, including most
prominently the spin ice materials. While these should not be
confused with hypothetical elementary monopoles existing in the
vacuum, they nonetheless have similar properties and can be probed
using similar techniques."The Anomalous Hall Effect and Magnetic Monopoles in Momentum
Space". Science 302 (5642) 92–95."Inducing a Magnetic Monopole with Topological Surface States"
and comments in articles about quasi-particles like this:
Many groups worldwide are currently researching the question of
whether magnetic whirls could be used in the production of computer
components.
led me to wonder what application might they have? Mixing these two concepts is probably a bad way to present this question. A true magnetic monopole would effect protons whereas the artificial ones don't.
What I don't understand is what advantages an artificial magnetic monopole would have. And does this relate to some theoretical aspect of a true monopole?
Best Answer
Many years ago I considered the situation of a genuine monopole continually threading through the middle of a wholly superconducting loop. So we have two interlocking Roman rings - one an electric charge circuit, the other a magnetic charge circuit. Depending on the relative sense of circulation, either the monopole gains energy at the expense of the supercurrent, or vice versa. Well actually, it might not be that simple.
Thing is, superconductivity is intimately associated with the usual vector potential A, and a supercurrent will only change in response to a change in an externally applied A. Such as to maintain the line integral of net A around the supercurrent invariant. But A is only generated by moving electric charge. The hypothetical 'back emf' of circulating monopole would be owing to an E field the analog of the B field of moving electric charge. On a time-average basis it would be steady given a steady monopole current. Hence of a fundamentally different character to an $E = -dA/dt$ owing to time-varying electric current, that the supercurrent would know and respect. Hence regardless of whether circulating monopole gains or loses energy in following along the lines of B generated by the supercurrent, the supercurrent itself will do squat. There is a similar dilemma when it comes to the predicted net force/torque balance - or rather imbalance.
Upshot is, one either accepts that energy-momentum conservation would dramatically fail, or take the scenario as proof that a genuine monopole cannot exist!